Electrochemical methods, devices and compositions

ABSTRACT

The disclosure provides a method comprising inducing a first current between a source of a countercharge and a first electrode, the first current being through an electrolyte. A second current is induced across the first electrode, the second current being transverse to the first current, and the second current inducing a relativistic charge across the first electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present continuation application claims priority to U.S.Nonprovisional application Ser. No. 15/649,633 titled “ElectrochemicalMethods, Devices and Compositions,” filed on Jul. 13, 2017, which claimspriority to U.S. Provisional Application No. 62/361,650 titled“Electrochemical Methods, Devices and Compositions,” filed on Jul. 13,2016, both of which are hereby incorporated by reference in theirentirety.

The present continuation application is related to U.S. Nonprovisionalapplication Ser. No. 15/649,569 titled “Electrochemical Methods, Devicesand Compositions,” filed on Jul. 13, 2017, which also claims priority toU.S. Provisional Application No. 62/361,650 titled “ElectrochemicalMethods, Devices and Compositions,” filed on Jul. 13, 2016, both ofwhich are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

Aspects of the present disclosure involve electrochemistry, andparticularly materials bonding, surface repair, electroplating,corrosion and electrocatalysis.

BACKGROUND

Traditional material fusion techniques, such as welding, have seriouslimitations. For example, often fusion techniques cannot be applied tomaterials with heat or electricity constraints. In one specific example,support beams are vulnerable to warping and possible failure when heatedto temperatures needed for traditional welding. In another example,objects near sensitive electronics and volatile chemicals cannot befused, re-fused or restored by conventional means (smelting, brazing,and welding) until separated from such sensitive equipment or materials.These methods also cannot be used on metallic materials which requirecontiguous, uniform properties.

Welding is a common method for fusing together metal pieces by heatingthe surfaces to the point of melting using a blowtorch, electric arc, orother means, and uniting the metal pieces by pressing, hammering, or thelike. Metals tend to be either machinable or weldable, which poses awidespread challenge in the manufacturing industry. For example, manyadvanced alloys are machinable, but conventional welding would altertheir precise grain structures and destroy the properties of the alloy.Welded and heat-treated joints experience changes to their materialproperties with consequences to stress and strain distribution, heatconduction, static dissipation, etc. As such, the conventional weldingis not compatible with all industrially relevant metals.

Alternatively, electrodeposition is a process for coating a thin layerof one metal on top of a substrate, often to modify its surfaceproperties. Although electrodeposition does not require the hightemperatures of welding for melting metal surface, the thin layers ofmetal obtained from electrodeposition cannot join and unite metal piecesin a mechanically strong or durable way.

It is with these issues in mind, among others, that aspects of thepresent disclosure were conceived.

SUMMARY

The following embodiments and aspects thereof are described andillustrated with systems, tools and methods meant to be exemplary andillustrative, not limiting in scope. In various embodiments, one or moreof the above-described problems have been reduced or eliminated, whileother embodiments are directed to other improvements.

Provided herein is a method comprising inducing a first current betweena source of a countercharge and a first electrode, the first currentbeing through an electrolyte. A second current is induced across thefirst electrode. The second current is transverse to the first current,and the second current inducing a relativistic charge across the firstelectrode. The method may further comprise applying a signalcancellation to reduce a far-field radiation from the first electrode.

The present disclosure also provides a method comprising inducing anelectric field between a source of a countercharge and a firstelectrode, the electric field having field lines through an electrolyte.A potential is induced across a surface of the first electrode. Theinduced potential bends the field lines proximate the surface such thatmetal from the electrolyte follows a path of the bent field lines todeposit the metal onto the surface.

The present disclosure further provides a method comprising inducing apotential across a surface of an electrode in the presence of a chemicalpotential between an electrolyte and the surface of the electrode. Theinduced potential relativistically charges the surface of the electrode.

The present disclosure provides a corroding electrode comprising one ormore metal species selected from the group consisting of metalparticles, metal ions, and combinations thereof. The corroding electrodedissolves when a first current is applied between the corrodingelectrode and a first electrode through an electrolyte, therebysuspending the one or more metal species into the electrolyte.

Provided herein is a device comprising a source of a countercharge, anda first electrode in electrical communication through an electrolytewith the source of a countercharge; wherein a first current is inducedthrough the electrolyte between the source of a countercharge and thefirst electrode; and wherein a second current is induced across thefirst electrode, the second current being transverse to the firstcurrent, and the second current inducing a relativistic charge acrossthe first electrode.

The present disclosure may also provide a device comprising a source ofa countercharge, and a first electrode in electrical communicationthrough an electrolyte with the source of a countercharge. An electricfield is induced between the source of a countercharge and the firstelectrode. The electric field has field lines through the electrolyte. Apotential is induced across a surface of the first electrode. Theinduced potential bends the field lines proximate the surface such thatmetal from the electrolyte follows a path of the bent field lines todeposit the metal onto the surface.

The present disclosure provides an electrode, wherein a potential isinduced across a surface of the electrode in the presence of a chemicalpotential between an electrolyte and the surface of the electrode. Theinduced potential relativistically charges the surface of the electrode.This electrode may be a first electrode in any method or devicedescribed herein.

The present disclosure further provides a device comprising a maincontrol unit comprising a power supply and a power modulator; anelectrode applicator unit, comprising at least one source of acountercharge and a plurality of channels for flowing an electrolytethrough the electrode applicator unit, the electrode applicator unitbeing connected to the main control unit; a current collector cableconnected to the main control unit; and a power control unit connectedto the main control unit. The power control unit applies a first currentbetween a first electrode and the at least one source of a counterchargethrough the electrolyte, the power control unit inducing a secondcurrent across the first electrode, the second current being transverseto the first current, and the second current inducing a relativisticcharge across the first electrode.

The present disclosure provides an apparatus, comprising: a source ofcountercharge; an electrode; an electrolyte in contact with theelectrode and through which a first current between the source ofcountercharge and electrode flows; and a waveform generating devicecoupled with the electrode, the waveform generating device inducing anelectric waveform across the electrode in the presence of the current.

The present disclosure provides a method, comprising applying a firstcurrent between a source of countercharge and an electrode; and applyingan electric waveform across the electrode, the electric waveform havingan energy density greater than 0 mA/cm² and less than 300 mA/cm² and afrequency between 35 kHz and 10 GHz.

Additional embodiments and features are set forth in part in thedescription that follows, and in part will become apparent to thoseskilled in the art upon examination of the specification, or may belearned by the practice of the embodiments discussed herein. A furtherunderstanding of certain embodiments may be realized by reference to theremaining portions of the specification and the drawings, which forms apart of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments are illustrated in referenced figures of thedrawings. It is intended that the embodiments and figures disclosed areto be illustrative rather than limiting.

FIG. 1A depicts a device 100 comprising a source of a countercharge 120,and a first electrode 110 in electrical communication with the source ofa countercharge 120 through an electrolyte 140. A first current 130 isinduced through the electrolyte 140 between the source of acountercharge 120 and the first electrode 110. A second current 150 isinduced across the first electrode 110, the second current 150 beingtransverse to the first current 130, and the second current 150 inducinga relativistic charge 112 across a surface 111 of the first electrode110. The device also comprises a power supply 160 in electricalcommunication 161 with the source for a countercharge 120 and inelectrical communication 162, 163 with the first electrode 110.

FIG. 1B is an inset of FIG. 1A, showing an embodiment where the sourceof countercharge 120 is a corroding electrode. When the first current130 is induced between the corroding electrode 120 and the firstelectrode 110 through the electrolyte 140, metal 122 from the corrodingelectrode 120 is released as metal species (M+) 124 into the electrolyte140.

FIG. 2 depicts a first electrode 110, wherein a potential 250 is inducedacross a surface 111 of the first electrode 110 in the presence of achemical potential 230 between an electrolyte 140 and the surface 111 ofthe first electrode 110. The induced potential 250 relativisticallycharges 112 the surface 111 of the first electrode 110.

FIG. 3 is a flowchart of the methods described. The workpiece may bepreprocessed (e.g., surface cleaning, roughening, etc.) (310), beforeinducing a first current (320) and inducing a second current (330). Ifthe electrochemical process is incomplete (340), the first currentand/or the second current may be modulated (350). If the electrochemicalprocess is complete (340), the process terminates (350).

FIG. 4A depicts capacitive charge separation 410 in a first electrode110. Electric field lines 135 are represented by black arrows pointingtoward negative charges (electrons, 420). FIG. 4B depicts electrondistribution 450 among the electrons 420 on smooth areas 430 and roughareas 440 of the surface 111 of the first electrode 110.

FIGS. 5A-5D depict several first electrodes with features filled byoperation of the methods described herein. In FIG. 5A, a second current150 transverse a first electrode 110 having a void 500 between a firstportion 113 and a second portion 114. The second current 150 produces arelativistic charge 112 on the first electrode 110, whereby metal isbonded to a first edge 115 and a second edge 116 to fill a gap 520 inthe void 500. FIG. 5B depicts a process similar to FIG. 5A, where thevoid 500 is a high-aspect ratio feature in the first electrode 110. InFIG. 5C, a rough surface 111 of the first electrode 110 is filled. FIG.5D is an inset of FIG. 5A showing the formation of a new metal-metalbond 530 between a metal 540 in the electrolyte 140, and a metal edge510 of the first edge 115 in the void 500.

FIGS. 6A-6C depict an electric field 600 inside a void 500 between twoportions 113, 114 of the first electrode 110. FIG. 6A shows the processwithout a second current 150; that is, a conventional electrodeposition.FIG. 6B shows application of a second current 150, without a DC offseton non-uniform surfaces. FIG. 6C shows the angles 151, 152, 153 of thesecond current 150 relative to the void 500. Arrows 611, 612, 613indicate directions of induced growth.

FIG. 7 depicts an electron distribution due to sinusoidal second current150.

FIGS. 8A-8B depict the effect of a second current 150 on the electricfield 135 of a first electrode 110 when surface electrons 420 are movingat constant, non-relativistic velocity (FIG. 8A) and at continuousacceleration (FIG. 8B), imparting a relativistic charge 112.

FIG. 9 depicts the properties of idealized waveform variations at 2Volts peak-to-peak (Vpp) and 2 Hz over two periods. These variations donot account for impedance. (*) The minor bumps depends upon theharmonics and waveform integrity produced by the signal generatingequipment. (†) Noise has no true period/frequency, and the actualproperties depend heavily upon the signal generating equipment and typeof noise.

FIG. 10 depicts device 1000 having a main control unit (MCU) 1020 and anelectrode applicator unit 1010.

FIGS. 11A and 11B depict a gun or wand type applicator 1100 from arepresentative section view (FIG. 11A) and from a top view (FIG. 11B),as an embodiment of an electrode applicator unit 1010.

FIGS. 12A and 12B depict a patch-type applicator 1200 from a top view(FIG. 12A) and from a side view (FIG. 12B), as an embodiment of anelectrode applicator unit 1010.

FIG. 13 depicts a glove-type applicator 1300, as an embodiment of anelectrode applicator unit 1010.

FIGS. 14A and 14B depicts a deposition from a saturated CuSO₄(aq) at 25°C., 30 mA/cm². Specifically, FIG. 14A was conducted without a secondcurrent; that is, a conventional electrodeposition). FIG. 14B wasconducted under a second current having a waveform of 5 MHz, 10 Vppsinusoidal.

FIGS. 15A and 15B depict a deposition of copper from 1.25 M CuSO₄(aq)electrolyte at 25° C. and 15 mA/cm² for 1 hour. Specifically, in FIG.15A no second current was applied; that is, it was a conventionalelectrodeposition. At FIG. 15B a second current of 1 MHz at 27 dbm (50Ω)was applied.

FIG. 16 depicts an electrochemical circuit pulsed adhesion scheme, whichmay be performed without a second current.

FIGS. 17A-17L depict an electrochemical corrosion followed bycrack-filling and planar surface deposition. FIG. 17A shows theelectrode 1700 with a surface having a cut 1710 and horizontalindentations 1720. FIGS. 17B and 17C show electrochemical corrosion androughening. FIGS. 17D-17L show the result of an electrochemical processusing a second current, providing in smooth, planar surface.

FIGS. 18A and 18B depict surface roughening of an originally smoothCu/FR1 surface in 1.25 M CuSO₄(aq) at 25° C. using second current at 7kV/30 mA (max limited) at 34 kHz (no counter electrode). FIG. 18A showsthe sample at ×200 magnification and FIG. 18B shows the same sample at×2000 magnification.

FIG. 19A depicts a corroding electrode formed from a pressed pelletcontaining Cu powder (about 10 μm average diameter) with 0.5% CuSO₄.

FIG. 19B presents the full view of the pellet. FIG. 19B is a microscopicview of the surface at ×800 magnification. Lighter areas at 10 μm Cupowder, darker areas are CuSO₄. Pellet pressed at 80 kpsi for 30 min.

FIG. 20 summarizes unit 2000 in action as welding device with wand typeapplicator 1100 and auxiliary leads 2030, 2035.

FIG. 21 shows the simulated electric field results for bothelectrodeposition and transverse currents in saltwater when the lowerworkpieces have a phase offset, phi of 0°.

FIG. 22 shows the simulated electric field results for bothelectrodeposition and transverse currents in saltwater when the lowerworkpieces have a phase offset, phi of 180°.

FIG. 23 shows the electric field oscillation minima and maxima duringdeposition at phi of 0°.

FIG. 24 shows the electric field oscillation minima and maxima duringdeposition at phi of 180°.

FIG. 25 shows the Transverse Current Right, Transverse Current Left, andthe electrodeposition current sent on separate channels.

FIG. 26 compares the original transverse current signals to the newcombined signal, where the Transverse Current Right, Transverse CurrentLeft, and the electrodeposition have been combined.

FIG. 27 shows combined left and right signals for the transversecurrent.

FIG. 28 shows that the parallel current imparted inside the junctionbetween the two pieces being joined is the same when comparing theoriginal transverse current signals to the combined transverse currentelectrodeposition signal.

FIG. 29 is an equation showing that an equivalent impedance is assumedwith transverse current and electrodeposition signals applied inparallel.

FIG. 30 shows the calculated potentials for ChA and ChB using theequivalent impedance.

FIG. 31 is an electron micrograph depicting a gap in a workpiece wheremetal grows faster at the edges facing the inside of the gap than fromthe bottom of the gap. The result of this growth are weak joints andpoor bonding.

FIG. 32 is also an electron micrograph depicting the poor joining of thetwo sides of a gap in a workpiece.

FIG. 33 is an SEM image of the bottom of a workpiece deposited withcopper using transverse current, oriented to what was the gap betweenthe joined pieces.

FIG. 34 is also an SEM image of the bottom a workpiece deposited withcopper using transverse current, oriented to show that the gap has beenfiled.

FIG. 35 was generated from a secondary electron detector, showingcontrast between surface textures.

FIG. 36 was generated from a backscattered electron detector, showingcontrast between the relative differences in atomic weight of differentelements.

FIGS. 37A-D are the elemental analysis for the samples in FIGS. 35 and36. Elemental mapping in FIG. 37A shows uniform copper distributionacross the two regions. Overall, oxygen concentration was low (FIGS. 37Cand D), but the oxygen levels were slightly greater on the bottom region(FIG. 37B).

FIGS. 38A-E shows aluminum particles embedded into an iron layer fromionic liquid. A vertical cross section of the sample was analyzed. FIG.38A shows the elements present. FIG. 38B was a composite of the iron,aluminum, and carbon signals, showing the codeposition of aluminum andiron at the surface of the steel substrate. FIGS. 38C-E are thetwo-dimensional elemental maps for iron, aluminum, and carbon,respectively.

FIGS. 39A-D shows the approximately 1:1 aluminum-iron alloy depositedfrom the ionic liquid onto copper. FIG. 39A is a scanning electronmicrograph of the sample. FIGS. 39B and 39C are the two-dimensionalelemental maps for aluminum and iron in the sample, respectively. FIG.39D shows the elements present in the sample.

FIGS. 40A-H show a 5:4 (mol/mol) iron-zinc alloy was deposited fromionic liquid. FIG. 40H shows an electron micrograph composite of theelectron micrograph (FIG. 40A), and the two-dimensional elementalcontents for iron (FIG. 40B), zinc (FIG. 40C), carbon (FIG. 40D),chlorine (FIG. 40E), and oxygen (FIG. 40F), showing the codeposition ofzinc and iron to form the alloy. FIG. 40G shows the elementaldistribution in the sample.

FIGS. 41A& B are photographs of copper bonded to carbon cloth fromconventional electrodeposition (FIG. 41A) and from the disclosed methodsusing a transverse current (FIG. 41B).

FIG. 42 is a photograph showing copper <110> joined to nickel <200> withcopper following the disclosed method.

FIG. 43A is a photograph showing brass joined with Al 7075 T6 withcopper following the disclosed method. FIG. 43B is a magnification ofthe joint between the brass and aluminum sections. FIG. 43C is aphotograph showing the workpiece after an additional round of depositionat the joint.

FIGS. 44A-E show copper workpieces joined with copper under differingconditions using the disclosed method. FIGS. 44A & 44B show coppersheets joined with the transverse current parallel to the junction.FIGS. 44C & 44D show copper sheets joined with transverse currentperpendicular to the junction. Here, a shiny finish was obtained, butthe junction displayed greater bending fatigue. FIG. 44E shows a sampledeposited without the transverse current as close to the junction andwith a 5-V DC offset, which displayed good strength and a rough finish.

FIG. 45 depicts the calculated electric energy distribution (V/m) acrossa workpiece under 1-GHz transverse current, where red and blue areasshow electric field strength at opposite polarities.

FIG. 46 depicts the calculated electric energy density time average(J/m³) across a workpiece under 1-GHz transverse current, where red isthe densest and dark blue is the least dense.

FIG. 47 depicts the calculated electric energy density time average(J/m³) across a workpiece under 1.35-GHz transverse current, where redis the densest and dark blue is the least dense.

FIG. 48 depicts the calculated electric energy density time average(J/m³) across a workpiece under 1.6-GHz transverse current, where red isthe densest and dark blue is the least dense.

FIG. 49 depicts the calculated electric energy density time average(J/m³) across a workpiece under 220-MHz transverse current, where red isthe densest and dark blue is the least dense.

FIG. 50 depicts the calculated electric energy density time average(J/m³) across a workpiece under 480-MHz transverse current, where red isthe densest and dark blue is the least dense.

DETAILED DESCRIPTION

Provided herein are methods, devices and compositions whichelectrochemically bond or rearrange metals on surfaces. Generally, themethods and devices operate by inducing a first current between a sourceof a countercharge and a first electrode through an electrolyte. Theelectrolyte is adjacent to the surface of the first electrode, formingan electrode-electrolyte interface, where metal from the electrolytecontacts the surface of the first electrode to form new metal-metalbonds during the electrochemical process.

The first electrode may be the workpiece where new metal-metal bonds areformed between metal on the surface and metal from the electrolyte, andis typically charged as a cathode. When a second, transverse current isinduced across the first electrode, electrons at the surface of theexperience a forward compression and rearward expansion of theirelectric field. This compression and expansion generates a relativisticcharge propagating outward from the electron's center at the speed oflight. The relativistic charge then bends the field lines of the firstcurrent, directing metal from the electrolyte to form new metal-metalbonds in cracks and crevices, pits and voids, and high-aspect surfacefeatures on the workpiece.

In contrast, in the example of a metal component with a crackconventional electrodeposition covers the top surface of the componentand domes over the crack, entombing a permanent crack. The methoddescribed herein, distinctly, fills in the gap and eliminates the crack,producing a flat joint and a workpiece with a flat backside. Moreover,metal at the boundaries of the crack may be bonded to metal from theelectrolyte in a mechanically robust way. In another embodiment, themethods disclosed herein fill in a through-hole drilled into aworkpiece, eliminating many steps from any suitable conventionalprocess. In other embodiments, the metal may be electroformed onto anegative mold. Conventionally, problems arise at the boundaries betweenmolded segments. The method disclosed here joins these molded segmentswith mechanically strong bonds.

The opposite effect may be attained by selecting the appropriatetransverse current, deterring filing effects. For example, a current maybe selected to prevent material from entering a gap in the workpiece,much as a current may be selected to corrode a region of a workpiece toroughen it for better adhesion in deposition.

The methods and devices described may operate by inducing an electricfield between a source of a countercharge and a first electrode wherethe electric field is through the electrolyte. The first electrode maybe workpiece on which or to which some operation, such as depositingmaterial, bonding, polishing, plating, or corrosion being performed,according to the techniques discussed.

An electric potential is induced across a surface of the firstelectrode. The induced potential bends the field lines proximate thesurface so metal from the electrolyte follows a path of the bent fieldlines to deposit the metal onto the surface. In one specific example,the induced potential affects the field lines. These bent field linesultimately intersect the surface, including irregularities in thesurface, at 90 degrees to the portion of the surface being intersected.Viewed another way, the bent field lines of the first current alter thetrajectory of the metal from the electrolyte as it deposits onto and isbonded to the surface, so the metal has a lower probability of reachingthe overall surface at 90° on its approach, but rather conforms to thecontours, irregularities, and exhibits a leveling behavior on thesurface.

The induced potential of the transverse current can be controlled bytuning the waveform, including its voltage, amperage and frequency.Multiple waveforms can even be combined to tune into different featuresor substances comprising the surface of the workpiece. The extent ofmetal bonding can be monitored in real-time, so the transverse currentand first current can be modulated to continue metal bonding,electropolishing, or other electrochemical processes on the workpiece.This electrochemical process can also be run in reverse, where corrosionof the workpiece sends metal species into the electrolyte. From eitherembodiment, the present methods and devices represent a radicaldeparture from conventional metal fusing techniques or previously knownelectrodeposition methods.

Specifically, conventional metal joining techniques use an adhesive withmaterial properties different from those of the substrate. Sometimessheet metal is joined by using advanced glues combined with crimping orrivets for strength, but these methods are limited to thin substrates.Fusion techniques such as welding use large amounts of power for heatand/or pressure to melt metal at junctions.

The welding techniques are cumbersome and dangerous. Many resistancewelding processes require an inert shielding gas to remove oxygen fromthe weld area. Gas compression is very inefficient and energy intensive,accounting for up to 10% of industrial electricity consumption. To avoidoverheating, welding is limited to a single spot or multiple spots onlyif sufficiently spaced. Resistance welding also involves intense UVradiation, deadly voltages and currents, toxic fumes, noise, andflammability concerns.

Welding has severe limitations to which metals to which it can beapplied. Welding dissimilar metals, even different grades of alloyhaving the same base metal, results in cracking and poor adhesion at thejoint. Many grades of common metals are non-weldable because of smallconcentrations of other elements which respond differently to intenseheat, such as aircraft grade aluminum (7075-T6), which contains ˜10% ofother elements including Zn and Cu.

Conventional electrodeposition may be used where welding fails, but notwithout its own limitations. Conventional electrodeposition does notform mechanically strong bonds between adjacent workpieces, due to metalsurface tension, contact resistance, and stored stress resistance (e.g.as shown at FIG. 6A). Conventional electrodeposition also employs large,typically aqueous, baths of plating solution and direct current appliedbetween an anode and a workpiece—an immersed, conductive cathode to bemetal-plated. Plating baths must be of very large volume (hundreds ofgallons) for even small workpieces to maintain homogenous reactantconcentrations, adequate spacing between the anode and workpiece, andcomplete peripheral anodic boundaries around the plated object to ensurea uniform electric field, and uniform plating on all sides of theobject.

As conventional deposition occurs, the concentration of dissolved metalspecies decreases approaching the electrode surface. Areas like trenchesand voids do not experience as much convection. They have lower reactantconcentrations and slower deposition rates compared to open surfaces.When this happens, like-charge repulsion increases. So long as positivemetal ions are abundant in solution to neutralize two adjacentnegatively-charged edges, metal depositing at each edge may grow towardone another, even to electrical contact. However, the growth of the twoedges into each other does not form a bond between them. They may growuntil the original surfaces abut each other, but the original gaps stillexists as a weak fracture that prevents mechanical resilience.

If the concentration of metal ions drops, the negative charges of eachedge are not neutralized and the two edges are repulsed from each other.With rough deposits, contact is poor, so edges are rough when theyinitially come into electric contact. The total contact area is low.This geometry contributes to contact resistance between metal edges thatgrow together and presents an energy barrier to forming strongmechanical contact. The energy to overcome the different stresses storedin each edge also increase.

During conventional electroplating, disproportionately more materialdeposits onto areas of curvature than on planar surfaces. A smooth, evenfinish is usually desired, so chemical and engineering controls must bebuilt into electroplating processes to reduce this effect. Controlsusually involve running the plating process at reduced currentdensities, using multiple, distributed anodes to shift the electricfield density, and using organic additives.

For conventional electrodeposition and plating, surfaces must bepreprocessed to achieve favorable outcomes. Acid strikes and polishingclean workpiece surfaces and remove native oxides that would otherwiseprevent newly deposited material from bonding. Low current densities areused to avoid rough deposits. These steps represent a significantportion of the chemical resources and time in conventionalelectroplating and deposition.

The present disclosure may be understood by reference to this detaileddescription, taken with the drawings as described above. It is notedthat, for illustrative clarity, certain elements in various drawings maynot be drawn to scale, may be represented schematically or conceptually,or otherwise may not correspond exactly to certain physicalconfigurations of embodiments.

I. Method

In view of the introduction, as well as issues and limitations relativeto conventional processes, provided herein are electrochemical apparatusand methods for depositing and rearranging metals on surfaces. FIG. 1illustrates an example device for practicing the method discussedherein. FIG. 3 illustrates an example method according to the presentdisclosure. Referring to FIGS. 1 and 3, a workpiece 110 may bepreprocessed (e.g., surface cleaning, roughening, etc.) (310), beforeinducing a first current (320) and inducing a second current (330),which may be an alternating or non-DC current across the workpiece. Ifthe electrochemical process is incomplete (340), the first currentand/or the second current may be modulated (350). If the electrochemicalprocess is complete (340), the process terminates (360). Thecompleteness of a reaction can be assessed by any method known to one ofskill in the art, including spectrometry and microscopy, as well asmethods newly disclosed herein, which monitor deposition in real-time.

Referring in more detail to FIG. 1, the device 100 involves a source ofa countercharge 120, and a first electrode 110 (which may be theworkpiece) in electrical communication with the source of acountercharge 120 through an electrolyte 140. A first current 130 isinduced through the electrolyte 140 between the source of acountercharge 120 and the first electrode 110. A second current 150 isinduced across the first electrode 110, the second current 150 beingtransverse to the first current 130, and the second current 150 inducinga relativistic charge 112 across a surface 111 of the first electrode110. In some embodiments, the device includes a power supply 161 inelectrical communication 161 with the source for a countercharge 120 andin electrical communication 162, 163 with the first electrode 110. Thepower supply, which may involve more than one physical power supplier,may provide and control the first current 130 and the second current150.

Alternatively, the methods according to this disclosure may becontemplated in a device according to FIG. 2. In this embodiment, afirst electrode 110 has a potential 250 induced across its surface 111in the presence of a chemical potential 230 between an electrolyte 140and the surface 111. The induced potential 250 relativistically charges112 the surface 111 of the first electrode 110. The induced potentialbends the field lines proximate the surface such that metal from theelectrolyte follows a path of the bent field lines to deposit and bondthe metal onto the material surface.

A. First Electrode (e.g., Workpiece)

The first electrode, in many possible examples discussed, may also bethe workpiece, or workpieces, or the cathode in an electrochemicalprocess. The first electrode may include more than one discrete piece,for example, when one is joining or bonding separate metal pieces.

At the first electrode, negative charge is isolated at a surface nearestthe electrolyte, while positive charge is pushed to the firstelectrode's farthest surfaces. The first electrode is polarized withnegative and positive charges when a current (for example, a firstcurrent or a transverse current) is applied, or when an electric orchemical potential is induced across the first electrode. The methodsaccording to this disclosure manipulate electron density on theworkpiece to guide metal deposition, and the like.

The charge density of a polarized workpiece absent the influence of asecond current can be understood referring to FIGS. 4A and 4B, whichillustrate the effects of smoothness and roughness on the substrate.Negatively charged sides 440 have a higher density of electrons 420,which distribute themselves evenly across the surface 111, due to theequal repulsion 460 of their individual electric fields. This repulsioneffect 460 occurs parallel to the tangential point of an electron'sposition at a surface 111. So smooth surfaces 430 experience the mostuniform charge distribution (FIG. 4A), whereas any curvature, such as arough topography, increases charge density (FIG. 4B). As curvature 440increases, the repulsive forces of local electrons are less in-plane,allowing closer proximity (FIG. 4B).

Continuing to reference FIGS. 4A and 4B, the electric field lines 135may originate at the source for a countercharge 120 and terminate at thenegatively charged surface 111 of the first electrode 110. The surface111 becomes negatively charged under operation of a current or aninduced potential. Electrons 420 have an electric field in alldirections (FIG. 4A), while electron-electron repulsion 460 occursparallel to the surface 111 (FIG. 4B). Due to electron distribution 450,electric field lines 135 terminate perpendicular to a tangent of thesurface 111 and deviate from their original vector (137) to maintainthis behavior at curves 440. The increased charge density at non-planarareas of the first electrode results in greater electrochemical activityrelative to smooth areas. The distance A between electrons 420 in smoothregions 430 is greater than the distance B between electrons 420 inrugged regions 440.

The workpiece may have voids and gaps, which affect the electrondistribution at the surface. Referring now to FIGS. 5A, 5B and 5D, thefirst electrode 110 may have a void 500 with a metal edge 510. Therelativistic charge 112 may cause a metal-metal bond 530 to form betweenmetal 540 from the electrolyte 140 and the metal edge 510 to fill thevoid 500. In various aspects, the void 500 may be a crack, crevice, orfracture in the first electrode. The void 500, of FIG. 5A is in the formof a gap 520 between a first portion 113 of the first electrode 110, thefirst portion 113 having a first edge 115 of the metal edge 510, and asecond portion 114 of the first electrode 110, the second portion 114with a second edge 116 of the metal edge 510 proximate the first edge114. The relativistic charge 112 may cause the metal-metal bond 530 toform between metal from the first edge 114 and metal 540 from theelectrolyte 140 and between metal from the second edge 116 and metal 540from the electrolyte 140. The bonded metals bridge the gap 520 to form aunified electrode of the first portion 114 and the second portion.

FIG. 5B depicts a process similar to FIG. 5A, where the void 500 is ahigh-aspect ratio feature in the first electrode 110. The void 500 herealso forms a gap 520 between a first portion 113 of the first electrode110, the first portion 113 having a first edge 115 of the metal edge510, and a second portion 114 of the first electrode 110, the secondportion 114 with a second edge 116 of the metal edge 510 proximate thefirst edge 115. The relativistic charge 112 causes the metal-metal bond530 (as shown in FIG. 5D) to form between metal from the first edge 115and metal 540 from the electrolyte 140 and between metal from the secondedge 116 and metal 540 from the electrolyte 140. The bonded metalsbridge the gap 520, with methods at the closing gap bonding, to form aunified electrode of the first portion 113 and the second portion 114,and metals bonded within and across the gap.

In FIG. 5C, a rough surface 111 of the first electrode 110 may be filledwith metal bonded from the electrolyte. The relativistic charge 112causes the metal-metal bond 530 to form between metal from the surface111 and metal 540 from the electrolyte 140. A chemical potential existsbetween the electrolyte and the surface of the workpiece. In thiscontext, a transverse current without applying a first current coulddrive some deposition, although the combination of a first current withthe transverse current is more effective at depositing more metal thanis lost to dissolution or corrosion.

The electrostatic environment of the voids described above can beunderstood with reference to FIG. 6A, illustrating a conventionalelectrodeposition process applied to the structure of FIG. 5A incontrast to FIG. 6B, illustrating a process as described herein appliedto the structure of FIG. 5A. Referring first to FIG. 6A, absent a secondcurrent 150, as in a conventional electrodeposition, void 500 within thefirst electrode 110 would have like charges and experience repulsion600. This interaction results in contact and stored stress resistance,which make strong bonding energetically unfavorable, such that metalfrom the electrolyte would not readily find its way into the void 500(FIG. 6A). While metal deposition may occur still inside the void 500,it would be slow compared to growth atop the surfaces 118, 119 closestthe source of a countercharge 120.

In contrast, now referring to FIG. 6A, using a method according to thepresent disclosure, a second current 150 flowing from a first portion113 to a second portion 114, across the first electrode 110 induces aplanar electric field in the void 500. The induced potential can betargeted across the area being treated or bonded; the potential need notbe induced across the entire workpiece. This electric field of thesecond current 150 transverses the first current. Depositing metalspecies are redirected by the second current 150 and fill the junction500 instead of immediately depositing on the surfaces 118, 119 of thefirst electrode 110 nearest to the source of a countercharge 120.

FIG. 6C illustrates possible angles 151, 152, 153 which the secondcurrent 150 could be applied relative to the void 500. Arrows 611, 612,613 indicate directions of induced growth. Angle 151 and arrow 611 wouldonly modulate the electrodeposition current and do not display thedisclosed effects related to treatment with a transverse current. Angle152 and arrow 612 would promote some additional growth within the gapcompared to a conventional electrodeposition, but not as much as angle153 and arrow 613, which squarely targets growth within void 500. Inpractice, applying and propagating a second current is complex. Theresults depend on more than just the angle, but also on frequency,power, and other characteristics of the second current.

B. Electrolyte

The methods and devices described herein use an electrolyte. Generally,the electrolyte comprises a metal, which is a source for new materialdeposited and bonded at the first electrode. In particular, theelectrolyte may comprise a metal and one or more species selected fromthe group consisting of water, ammonium salts, metal chlorides, metalsulfates, ionic liquids, ionogels, and any combination thereof. When theelectrolyte comprises an ammonium salt, the ammonium salt may be atertiary ammonium salt, a quaternary ammonium salt, or combinationsthereof.

1. Solvent

Generally, the electrolyte comprises one or more solvents. The solventmay comprise water, an organic solvent, or ionic liquids. In particular,non-aqueous solutions may include deep eutectic solvents, ionic liquids,room temperature ionic liquids (RTIL), ionogels, and other organicsolvents, which support ionic conductivity and metal dissolution.

When present, the organic solvent may be a polar protic solvent, a polaraprotic solvent, a non-polar solvent, or combinations thereof. Suitableexamples of polar protic solvents include, but are not limited toalcohols such as methanol, ethanol, isopropanol, n-propanol, isobutanol,n-butanol, s-butanol, t-butanol, and the like; diols such as propyleneglycol; organic acids such as formic acid, acetic acid, and so forth;amines such as trimethylamine, or triethylamine, and the like; amidessuch as formamide, acetamide, and so forth; and combinations of theabove.

Non-limiting examples of suitable polar aprotic solvents includeacetonitrile, dichloromethane (DCM), diethoxymethane,N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), N,N-dimethylpropionamide,1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (DMPU),1,3-dimethyl-2-imidazolidinone (DMI), 1,2-dimethoxyethane (DME),dimethoxymethane, bis(2-methoxyethyl)ether, 1,4-dioxane,N-methyl-2-pyrrolidinone (NMP), ethyl formate, formamide,hexamethylphosphoramide, N-methylacetamide, N-methylformamide, methylenechloride, nitrobenzene, nitromethane, propionitrile, sulfolane,tetramethylurea, tetrahydrofuran (THF), 2-methyltetrahydrofuran,trichloromethane, and combinations thereof.

Suitable examples of non-polar solvents include, but are not limited to,alkane and substituted alkane solvents (including cycloalkanes),aromatic hydrocarbons, esters, ethers, combinations thereof, and thelike. Specific non-polar solvents that may be employed include, forexample, benzene, butyl acetate, t-butyl methylether, chlorobenzene,chloroform, chloromethane, cyclohexane, dichloromethane, dichloroethane,diethyl ether, ethyl acetate, diethylene glycol, fluorobenzene, heptane,hexane, isopropyl acetate, methyltetrahydrofuran, pentyl acetate,n-propyl acetate, tetrahydrofuran, toluene, and combinations thereof.

A electrolyte comprising organic solutions frequently exhibit greaterviscosity, which can cause slower molecular diffusion but benefits fromincreased particle suspension capacity. Electrolyte having organicsolvent may also display much larger electrochemical windows (2 V to 6V), compared to water (about 1.23 V). Organic solvents may also havegreater operating temperature ranges above the 100° C. limit for aqueoussystems. Generally, organic solutions do not codeposit with the metalduring deposition. Organic solvents also allow deposition of morereactive metals, including pure Fe and Al. For at least these reasons,some electrolytes may comprise an organic solvent.

In other embodiments, the electrolyte may comprise an ionic liquid, suchas a room-temperature ionic liquid (RTIL), which are relativelynon-volatile, highly tunable molten salts whose melting points are belowambient temperature. RTILs are solvents with low viscosities (10-100cP), low melting points, a range of densities, and relatively smallmolar volumes. Generally, RTILs consist of a cation and an anion.

The cation in the RTIL may include, but is not limited to, imidazolium,phosphonium, ammonium, and pyridinium. In particular embodiments, theRTIL comprises an imidazolium cation; that is, the RTIL is animidazolium-based ionic liquid. Each cation may be substituted with oneor more R groups, such as an imidazolium having the formula [Rmim] or[R₂mim], wherein “mim” references the imidazolium. The R group maycomprise one or more n-alkyl, branched alkyl, alkenyl, such as vinyl orallyl, alkynyl, fluoroalkyl, benzyl, styryl, hydroxyl, ether, amine,nitrile, silyl, siloxy, oligo(ethylene glycol), isothiocyanates, andsulfonic acids. In particular, the R group may be an alkyl selected frommethyl or ethyl.

The RTIL may be functionalized with one, two, three, or moreoligo(alkylene glycol) substituents, such as an oligo(ethylene glycol).Alternatively, the oligo(alkylene glycol) may be a methylene glycol or apropylene glycol. A vicinal diol substituent on the RTILs may providegreater aqueous solubility and possible water miscibility. PolymerizableRTILs may be provided choosing one or more R groups on the cation from astyrene, vinyl, allyl, or other polymerizable group.

Examples of suitable cations in the RTIL include, but are not limitedto, 1-ethyl-3-methyl imidazolium ([EMIM]), 1-hexyl-3-methyl imidazolium([HMIM]), 1-vinyl-3-ethyl-imidazolium ([VEIM]),1-allyl-3-methyl-imidazolium ([AMIM]), 1-hexyl-3-butyl-imidazolium([HBIM]), 1-vinyl-3-methylimidazolium ([VMIM]),1-hydroxyundecanyl-3-methylimidazolium ([(C₁₁OH)MIM]),tetrabutylphosphonium ([P4444]), 1-(2,3-dihydroxypropyl)-alkylimidazolium ([(dhp)MIM]), and combinations thereof. For example, thecation may be 1-ethyl-3-methyl imidazolium ([EMIM]). The cation may be1-hexyl-3-methyl imidazolium ([HMIM]). The cation may be1-vinyl-3-ethyl-imidazolium ([VEIM]). The cation may be1-allyl-3-methyl-imidazolium ([AMIM]). The cation may be1-hexyl-3-butyl-imidazolium ([HBIM]), 1-vinyl-3-methylimidazolium([VMIM]). The cation may be 1-hydroxyundecanyl-3-methylimidazolium([(C₁₁OH)MIM]). The cation may be tetrabutylphosphonium ([P4444]). Thecation may also be 1-(2,3-dihydroxypropyl)-alkyl imidazolium([(dhp)MIM]).

Suitable anions (X) in the RTIL include, but are not limited to,chloride (Cl), bromide (Br), iodide (I), triflate (OTf), dicyanamide(DCA), tricyanomethanide (TCM), tetrafluoroborate (BF₄),hexafluorophosphate (PF₆), taurinate (Tau), andbis(trifluoromethane)sulfonimide (TSFI). For example, the anion may betriflate (OTf). The anion may be dicyanamide (DCA). The anion may betricyanomethanide (TCM). The anion may be tetrafluoroborate (BF₄). Theanion may be hexafluorophosphate (PF₆). The anion may be taurinate(Tau). The anion may be bis(trifluoromethane)sulfonimide (TFSI).

Any combination of cations and anions described may form a suitableRTIL. Examples of suitable RTILs include, but are not limited to,1-ethyl-3-methyl imidazolium bis(trifluoromethane)sulfonamide([EMIM][TFSI]), 1-hexyl-3-methyl imidazoliumbis(trifluoromethane)sulfonamide ([HMIM][TFSI]),1-vinyl-3-ethyl-imidazolium bis(trifluoromethane)sulfonamide ([VEIM][TFSI]), 1-allyl-3-methyl-imidazolium bis(trifluoromethane)sulfonamide([AMIM][TFSI]), 1-hexyl-3-butyl-imidazoliumbis(trifluoromethane)sulfonamide ([HBIM][TFSI]),1-vinyl-3-methylimidazolium bis(trifluoromethane)sulfonamide ([VMIM][TFSI]), 1-hydroxyundecanyl-3-methylimidazoliumbis(trifluoromethane)sulfonamide ([(C₁₁OH)MIM][TFSI]),1-ethyl-3-methylimidazolium tricyanomethanide ([EMIM][TCM]),tetrabutylphosphonium taurinate, ([P4444][Tau]),1-ethyl-3-methylimidazolium dicyanamide ([EMIM][DCA]),1-(2,3-dihydroxypropyl)-alkyl imidazolium dicyanamide ([(dhp)MIM][DCA]), 1-(2,3-dihydroxypropyl)-3-alkyl imidazolium tetrafluoroborate([(dhp)MIM][BF₄]), 1-(2,3-dihydroxypropyl)-3-alkyl imidazoliumbis(trifluoromethane)sulfonimide ([(dhp)MIM][TFSI]),1-(2,3-dihydroxypropyl)-3-alkyl imidazolium hexafluorophosphate([(dhp)MIM][PF₆]), or combinations thereof. In particular, theroom-temperature ionic liquid may be 1-ethyl-3-methylimidazoliumchloride (EMIC). Exemplary RTILs are further illustrated below at Table1.

TABLE 1 Exemplary RTILs. Abbreviation Chemical Name Structure EMIC,[EMIM][Cl] 1-ethyl-3-methylimidazolium chloride

[EMIM][TSFI] 1-ethyl-3-methylimidazoliumbis(trifluoromethane)sulfonimide

[VEIM][TSFI] 1-vinyl-3-ethyl-imidazoliumbis(trifluoromethane)sulfonimide

[HMIM][TSFI] 1-hexyl-3-methyl-imidazoliumbis(trifluoromethane)sulfonimide

[AMIM][TSFI] 1-allyl-3-methyl-imidazoliumbis(trifluoromethane)sulfonimide

[HBIM][TSFI] 1-hexyl-3-butyl-imidazoliumbis(trifluoromethane)sulfonimide

[VMIM][TSFI] 1-vinyl-3-methylimidazoliumbis(trifluoromethane)sulfonimide

[(C₁₁OH)MIM] [TSFI] 1-hydroxyundecanyl-3- methylimidazoliumbis(trifluoromethane)sulfonimide

[EMIM][TCM] 1-ethyl-3-methylimidazolium tricyanomethanide

[P4444][Tau] tetrabutylphosphonium taurinate

[EMIM][DCA] 1-ethyl-3-methylimidazolium dicyanamide

[DMIM][Tf2N] or [DEIM][Tf2N] 1-(2,3-dihydroxypropyl)-3-methylimidazolium bis(trifluoromethanesulfonimide) or1-(2,3-dihydroxypropyl)-3- ethylimidazoliumbis(trifluoromethanesulfonimide)

[DMIM][BF4] or [DEIM][BF4] 1-(2,3-dihydroxypropyl)-3- methylimidazoliumtetrafluoroborate or 1-(2,3-dihydroxypropyl)-3- ethylimidazoliumtetrafluoroborate

[DMIM][DCA] or [DEIM][DCA] 1-(2,3-dihydroxypropyl)-3- methylimidazoliumdicyanamide or 1-(2,3-dihydroxypropyl)-3- ethylimidazolium dicyanamide

[DMIM][PF6] or [DEIM][PF6] 1-(2,3-dihydroxypropyl)-3- methylimidazoliumhexafluorophosphate or 1-(2,3-dihydroxypropyl)-3- ethylimidazoliumhexafluorophosphate

In other embodiments, the electrolyte may comprise an ionic liquid orcomposition disclosed in co-pending U.S. application Ser. No.15/293,096, filed Oct. 13, 2016, and entitled “Metal Deposits,Compositions, Methods for Making the Same,” the entire disclosure ofwhich is incorporated herein by reference in its entirety for allpurposes.

The electrolyte may comprise a mixture of water and an RTIL. For suchmixtures, the volume ratio may be between about 99:1 and about 1:99water/RTIL, such as between about 99:1 and about 95:5 water/RTIL,between about 95:5 and about 90:10 water/RTIL, between about 90:10 andabout 85:15 water/RTIL, between about 85:15 and about 80:20 water/RTIL,between about 80:20 and about 75:25 water/RTIL, between about 75:25 andabout 70:30 water/RTIL, between about 70:30 and about 65:35 water/RTIL,between about 65:35 and about 60:40 water/RTIL, between about 60:40 andabout 55:45 water/RTIL, between about 55:45 and about 50:50 water/RTIL,between about 50:50 and about 55:45 water/RTIL, between about 55:45 andabout 45:65 water/RTIL, between about 45:65 and about 40:60 water/RTIL,between about 40:60 and about 35:65 water/RTIL, between about 35:65 andabout 30:70 water/RTIL, between about 30:70 and about 25:75 water/RTIL,between about 25:75 and about 20:80 water/RTIL, between about 20:80 andabout 15:85 water/RTIL, between about 15:85 and about 10:90 water/RTIL,between about 10:90 and about 5:95 water/RTIL, or between about 5:95 andabout 1:99 water/RTIL. In particular, the molar ratio may between about70:30 and about 20:80 water/RTIL, between about 60:40 and about 30:70water/RTIL, or at about 40:60 water/RTIL. In another example, theelectrolyte may only contain a trace amount of water, such as thatabsorbed from the atmosphere. That is, the electrolyte may besubstantially non-aqueous.

The electrolyte may have at a temperature above 0° C. and below about250° C., such between about +0° C. and about 10° C., between about 10°C. and about 20° C., between about 20° C. and about 30° C., betweenabout 30° C. and about 40° C., between about 40° C. and about 50° C.,between about 50° C. and about 60° C., between about 60° C. and about70° C., between about 70° C. and about 80° C., between about 80° C. andabout 90° C., between about 90° C. and about 100° C., between about 100°C. and about 110° C., between about 110° C. and about 120° C., betweenabout 120° C. and about 130° C., between about 130° C. and about 140°C., between about 140° C. and about 150° C., between about 150° C. andabout 160° C., between about 160° C. and about 170° C., between about170° C. and about 180° C., between about 180° C. and about 190° C.,between about 190° C. and about 200° C., between about 200° C. and about210° C., between about 210° C. and about 220° C., between about 220° C.and about 230° C., between about 230° C. and about 240° C., betweenabout 240° C. and about 250° C., between about 250° C. and about 260°C., between about 260° C. and about 270° C., between about 270° C. andabout 280° C., between about 280° C. and about 290° C., or between about290° C. and about 300° C.

The pH of the electrolyte may vary depending upon the embodiment.Different metals and composites typically have pH requirements tomaintain a stable mixture in solution. The wetting characteristics ofsurfactant maintain its presence at the first electrode/electrolyteinterface. Therefore, the surfactant may also buffer against thedramatic pH gradients that occur between the interface and theelectrolyte bulk due to proton consumption and metal hydroxideprecipitation on the substrate.

The dielectric constant of the electrolyte is responsible for how a wavepropagates through the medium. The higher the constant, the morecompressed the wave and the slower its travel time. Low dielectricconstants allow fast travel near the speed of light. Electrolytes areconductive, taking and dissipating energy from the wave as itpropagates. As such the parameters of the current are adjusted toaccount for the dielectric constant. In water, about 11% speed of lightwith dielectric of about 80. RTILs have a dielectric constant of about40, and air a constant of about 1.

2. Metal

Generally, the electrolyte comprises metal. The metal may be metalparticles, such as dissolved or suspended metallic micro- ornanoparticles, or molecular metal ions, such as dissolved metal salts.Examples of suitable metals include, but are not limited to, zinc,cadmium, copper, nickel, chromium, tin, gold, silver, platinum, lead,ruthenium, rhodium, palladium, osmium, iridium, iron, cobalt, indium,arsenic, antimony, bismuth, manganese, rhenium, aluminum, zirconium,titanium, hafnium, vanadium, niobium, tantalum, tungsten, andmolybdenum. Examples of suitable alloys having two metals include, butare not limited to gold-copper-cadmium, zinc-cobalt, zinc-iron,zinc-nickel, brass (an alloy of copper and zinc), bronze (copper-tin),tin-zinc, tin-nickel, and tin-cobalt.

In some embodiments, the electrolyte comprises metal particles.Deposition of metal particles of a desired composition, crystallinityand crystal structure may provide same or substantially similarproperties to the deposited material on the first electrode with lessdependence upon specific deposition parameters. Each metal particlebrings millions of preformed metal bonds, resulting in proportionalityless energy needed from the first current to complete the bondingdeposit compared to conventional electrodeposition. The particle volumealso dramatically accelerates the bonding deposition rate. At least forthese reasons, particle codeposition improves the time and energyefficiency of the methods disclosed herein.

In contrast, conventional electrodeposition is very slow becauseindividual metal atoms must migrate through liquid to the metal surfaceto deposit, one by one. Without wishing to be bound by theory, whenmetal particles electrically contact the first electrode, dissolvedmetal species also deposit on and around the metal particle inbrick-and-mortar fashion until the metal particle is completelyoccluded. Before occlusion, however, the metal particle itself does notchemically bond to the first electrode unless its surface atoms are in areducible state. As such, depositing molecular species push away themetal particles from the surface instead of becoming occluded. Metalparticles that occlude may have trapped electrolyte between them and thesurface. This porosity is detrimental to the mechanical integrity of thedeposit. Conventional electrodeposition rarely occludes over 10 vol %metal particles.

The composition of the metal particles may match that of the firstelectrode. Metal particles of two or more elements, such as Al and Fe,may be mixed in a desired stoichiometry to yield an alloy. Mixed metalparticles may codeposit an element poorly soluble in the electrolyte orfor which reduction to a metallic state is outside the electrochemicalpotential window of the electrolyte. For example, aluminum ismolecularly reducible in EMIC, while iron is not. Ceramic or polymerparticles may be codeposited with metal particles to obtain depositproperties outside the range or alterability of a base metal alone.

Particles of dielectric polymers may be codeposited to modify thedielectric properties of the deposit, or to increase deposition ratewithout increasing the potential for surface roughness (molecularspecies deposit around dielectric particles, and atop conductiveparticles leading to roughness with the latter).

The electrolyte may comprise a metal salt. Any metal salt known withinthe electrochemical arts is suitable for this method.

3. Additives

The electrolyte may further comprises one or more additives, includingbut not limited to, acids, bases, salts, surfactants, thickeners,buffers, ionizable organic compounds, and fibers. In particular, theelectrolyte may comprise thickener to modulate the viscosity andincrease the mass of particulates stably suspended in the liquidelectrolyte.

In some embodiments, the electrolyte may comprise fibers. Fibers mayincrease the mass electrodeposited on the first electrode per time percharge applied between the first electrode and source of acountercharge. Fibers suspended within the electrolyte may becodeposited with metals at the first electrode to modulate themechanical properties of the deposited material. Fibers based uponcarbon, silicon or other materials may modify the tensile strength,ductility, or other properties.

In other embodiments, the electrolyte may comprise a surfactant. Thesurfactant, when present, may be sodium dodecyl sulfate (SDS), ammoniumlauryl sulfate, or a block copolymer, such as polyethylene glycol. Inparticular sodium dodecyl sulfate may be mixed with alkali to reduce theadsorption strength between the surfactant and the surface.Alternatively, the ionic sulfate headgroup of SDS may be replaced withsulfamate to achieve this effect without increasing alkali content.

In a polar solutions, concentrations of surfactant above the criticalmicelle concentration (CMC) result in micelles, which may encapsulateparticulates to increase their effective solubility and mass loading,and to insulate suspended particles from the oxidizing effects ofwater-induced passivation and corrosion. Surfactants may also mitigatedendritic nucleation and growth, resulting in a more even depositionacross the first electrode. Surfactants may decrease the firstelectrode's surface energy and facilitate removal of hydrogen bubbles toavoid pits and pores than can otherwise form in the deposited material.Surfactants may also brighten by inhibiting the buildup of more oxidizedspecies such as Fe⁺³, removing the need for post-treatments normallyrequired to provide a polished surface.

While protecting suspended or dissolved particles against oxidation, asurfactant shell can itself be an energy barrier to electrodeposition.Additional overpotential may be needed to decompose the surfactant sothat charge transfer may reach the particle surface. Long and shortchain surfactants with electrically conductive backbones may loweroverpotentials associated with surfactant.

The range of concentration of additives in the electrolyte can and willvary. Generally the concentration of additives in the electrolyte mayrage between about 10⁻² mol/L and about 10⁻⁵ mol/L, such as betweenabout 10⁻² mol/L and about 10⁻³ mol/L, between about 10⁻³ mol/L andabout 10⁻⁴ mol/L, or between about 10⁻⁴ mol/L and about 10⁻⁵ mol/L.

When present, the concentration of surfactant within the electrolyte maybe much greater than that of other additives. If the additive is asurfactant that can be incorporated into the deposit on the firstelectrode, the surfactant concentration should be minimized in theelectrolyte by balancing the smallest concentration of surfactant withthe average chain length of surfactant. Long-chain neutral surfactantsare typically more effective at increasing the viscosity of a solution,but may decrease the diffuse mobility of encapsulated particles.Short-chain ionic surfactants may increase the diffuse mobility ofencapsulated particles, while enhancing the ionic conductivity of thesupporting solution.

C. Source of a Countercharge

The methods and devices of the present disclosure may also comprise asource of a countercharge. When present, referring to FIG. 1A, thesource of a countercharge 120 may be an electrode counter to the firstelectrode 110, where the first current 130 is induced between the firstelectrode 110 and the source of a countercharge 120. The source of acountercharge generally provides an anode for an electrochemical processdescribed herein.

In some embodiments, the source of a countercharge may a non-corrodingelectrode, which is generally stable during induction of a firstcurrent. That is, the non-corroding electrode does not dissolve orrelease metal into the electrolyte because of a chemical potentialbetween it and the electrolyte, or because of an electric potentialbetween the source for a countercharge and the first electrode.

Suitable examples of non-corroding electrodes include, but are notlimited to, Pt, Au, boron-doped diamond, or platinized or gold-coatedconductive substrate. Suitable soluble electrodes include, but are notlimited to, Fe, Al, Cu, or any other electrically conductive metal,including alloys and composites. Electrodes may be interchangeable tofacilitate routine replacement and maintenance and reconfiguration.Although presented here in the source of a countercharge, non-corrodingelectrodes may also be electrodes in other capacities, includingcathodes and reference electrodes.

In other embodiments, the source of a countercharge may be a corrodingelectrode, which dissolves when a first current is applied between thecorroding electrode and a first electrode through an electrolyte,suspending the one or more metal species into the electrolyte. Referringto FIG. 1B, a corroding electrode is depicted as a possible source of acountercharge. When the first current 130 is induced between thecorroding electrode 120 and the first electrode 110 through theelectrolyte 140, metal 122 from the corroding electrode 120 is releasedas metal species (M⁺) 124 into the electrolyte 140. Additional metal canbe in the electrolyte when the electrode is corroding, for example frommetal salts dissolved in the electrolyte. In other instances, the onlymetal source is from metal species released from the corrodingelectrode.

In various embodiments, a corroding electrode may comprise one or moremetal species selected from the group consisting of metal particles,metal ions, and combinations thereof. Dissolving the corroding electrodereleases new metal into the electrolyte, maintaining its concentrationthrough the duration of the method. The metal-carrying capacity of theelectrolyte becomes less important because fresh metal can be suppliedfrom dissolution of the corroding electrode. Metal precursors aresupplied from the controlled corrosion of a formulated source of acountercharge into the electrolyte near the first electrode.

The corroding electrode may further comprise one or more ceramicparticles or dielectric polymers. The corroding electrode may be formedby pressing together metal particles into a solid body, with or withoutbinding agents. The corroding electrode may be made by any number ofthermal, pressure, or chemical synthesis methods. In one instance, thecorroding electrode may be made by pressing metal powders into anelectrode geometry, such as a rod for gun-feed style applicators, or asa disk-pellet for patch style applicators. In some instances metaland/or composite powder may be mixed in a vial, added to the inside adie in a hydraulic press, pressed together, and removed as a metalpellet for use an as a corroding anode.

The corroding electrode may comprise one or more sizes and geometries ofparticles. During deposition, corrosion of the source of a counterchargemay occur primarily along the grain boundaries of the pressed particleswhen higher current densities are used, causing their release intosolution with their approximately original dimensions. Particlesdissolved in this way are surface activated and exhibit a highersolubility in the electrolyte than particles simply mixed into solution.Particles with a surrounding layer of metal-species which iselectroactive for deposition, such as Al₄Cl₇ in1-ethyl-3-methylimidazolium chloride (EMIC), are more readilycodeposited.

The metal particles may have grain sizes selected to grain sizes of thefirst electrode. Metal particle size may be small enough to remainsuspended in the electrolyte and avoid the effects of gravity or controlthe impact of grain size on the properties of the deposit. Larger grainsresult in a harder metal from a slower process. Smaller grains yieldsofter metal with more ductility from a faster deposition. The largerthe discrepancy at the grain boundary defines points of failure.

Grain sizes may be selected to match those of the substrate, helpingincrease continuous uniformity between the substrates. New metalstrongly fills gaps in the workpiece along the metal line. Pores areclosed in the deposition. The former gap is superimposed with newmaterial defined by an elongated grain structure and high aspect ratios.This morphology is structured by the waveform of the transverse current.

In some embodiments, the metal particles may have rough or non-symmetricdimensions. In other embodiments, the metal particles may have sphericaldimensions and a uniform surface energy. In still other embodiments, themetal particles may have an elongated dimension, which aligns with asecond current induced across the first electrode, the second currentbeing transverse to the first current, and the second current inducing arelativistic charge across the first electrode.

Without wishing to be bound by theory, rough or non-symmetric particlesmay be more easily suspended in solution and can be codeposited in yieldhigher than symmetric particles. Spherical particles with uniformsurface energy may codeposit such that the overall finish of the depositis more predictable and easy to control. Elongated particles may alignthemselves with the electric or magnetic fields of second current andencourage directional growth, bridging a gap between two firstelectrodes more rapidly.

D. First Current (Electric Field)

Using the methods described herein, referring to FIG. 1A, the firstcurrent 130 is an induced current between the source of thecountercharge 120 and the first electrode 110 through the electrolyte140. The first current 130 may the result of an electric field betweenthe source of the countercharge 120 and the first electrode 110 throughthe electrolyte 140. The first current polarizes the workpiece so thatit possesses a net negative charge. This negative charge effects acharge transfer reaction with dissolved and suspended metal ions andparticles from the electrolyte to effect new metal-metal bonds withmetals on the surface of the workpiece.

The first current may be modulated in its power, voltage, amperage,frequency, duration, and other parameters. The first current may beinduced using a pulse plating or a reverse-pulse plating scheme, where apulsed power is applied to sequences of galvanostatic, galvanodynamic,potentiostatic, and potentiodynamic power to the first electrode throughthe first current. Such pulses may be applied in a repeating sequence.

Shorter pulses of polarization of the workpiece may maintain arelatively stable concentration balance of the metal species at theworkpiece/electrolyte interface. Dissolved metal salts and suspendedmetal particles in an electrolyte have different diffusion rates andrequire different energies to electrophoresis. As the metal speciesapproach the surface of the workpiece, concentration of metal salts andmetal particulate become imbalanced compared to the bulk electrolyte.Because the metal salts diffuse more quickly than metal particles, theyreach the surface at a faster rate and are more likely to be deposited.Shorter pulses of polarization allows these metal species to equilibrateduring the electrochemical process.

Pulse plating or reverse-pulse plating schemes through the first circuitsmoothen the surface and retard deposition. Pulse plating typically usesan on-off pulse rather than a sine wave. The off cycle allows freshelectrolyte to diffuse into features on the workpiece. The on cycledrives deposition onto the workpiece. The primary benefit of pulseplating is that the off-cycles of the pulse allow more time forconvection of the electrolyte near the surface. This can restore a moreuniform concentration of fresh reactants across the surface despitefaster depletion at rough areas during the on cycle. During the ONperiod, rough areas still experience higher charge density than smoothareas and so the benefit of pulse plating has limitations. Sequences ofpulses of opposite polarity may increase the adhesion and mechanicalstrength of deposited metal, by promoting a greater number ofmetal-metal bonds.

Pulses may include dynamic current or potential ramp rates, for examplea pulse applied at about 5 mA/μs from between about 0 mA and about 2 mA,followed by −0.2 mA/μs from between about 2 mA and about 0 mA. Pulsesmay involve uniform or disproportional changes in polarity, for examplea pulse with lower and upper bounds of between about −1.5 V and about1.5 V, or between about −1.5 V and about 0.7 V. These pulses may begenerated from an electroplating power supply, which may be power supply160, or a reverse pulse rectifier used to generate a DC current forelectrochemical processes.

When used, pulse plating occurs over a defined period, such as 1 to 1000microseconds for aqueous electrolytes. The period may be static, wherethe same time interval spaces each pulse, or it may be dynamic, wherethe periods change between each pulse. The length of the period may belonger for electrolytes that are more viscous.

For example, referring to FIG. 3, preprocessing the first electrode mayinvolve positively polarizing the first electrode to corrode the surfaceof the first electrode into the electrolyte (310). Preprocessing maythen be followed by a negative polarization, which electrodeposits morematerial onto the first electrode than was corroded off in the previousstep (320). The negative polarization may then be followed by inductionof a second current transverse to the first current of the negativepolarization (330). The completeness of the electrochemical process maybe assessed (340). If the electrochemical process is not complete, thefirst current and/or the second current are modulated the desiredmaterial was deposited while assuring superior surface penetration(350). If the electrochemical process is complete, the process isterminated (360).

A similar sequence might also continuously corrode and redepositmaterial from the surface of particles already deposited onto the firstelectrode. This approach could homogenize the surface and increasebonding across the entire surface boundary of deposited particles. Inthis way, an initial sequence of pulses may clean the surface of thefirst electrode.

A final sequence of pulses may be affected to passivate (or pickle) thesurface of the first electrode. Electropolishing, when used, may leavethe deposited material with the corrosion resistance finish. Pulsedpower may decrease the lattice strain and surface roughness of depositedmetal. For deposits with thickness around 1 millimeter or more,mitigation of lattice strain is less important because fractures afterseveral micrometers of deposit are eventually filled-in with morematerial.

E. Second (Transverse)Current (Induced Potential)

Following the methods described herein, referring to FIGS. 1A, 2, and6B, a second current 150 (which current may be from an induced potential250) can be applied through and/or across the surface 111 of the firstelectrode 110 to affect surface electrons 420 and induce favorableproperties in the deposit without altering the parameters of the firstcurrent 130, the electrolyte 140 or the source of a countercharge 120.The electrons 450 at the surface 111 experience a forward compressionand rearward expansion of their electric field. This compression andexpansion generates a relativistic charge 112 propagating outward fromthe electron's center at the speed of light. The relativistic chargethen bends the field lines of the first current 130, directing metalfrom the electrolyte to form new metal-metal bonds on the firstelectrode.

Viewed in another way, the induced potential bends the field linesproximate the surface so metal from the electrolyte follows a path ofthe bent field lines to deposit the metal onto the surface. The bentfield lines ultimately intersect the surface, including irregularitiesin the surface, at 90 degrees within close proximity to the portion ofthe surface being intersected. The difference between a point ofdeposition under the induced potential and a point of deposition withoutthe induced potential is a shift of the field lines toward crevices andrough areas of the surface not normally filled.

The second current can augment many aspects of electroplating andelectrodeposition processes, including, but not limited to,two-dimensional growth (smoothness and uniformity); grain properties,such as crystallinity and morphology; induced nucleation onenergetically difficult surfaces; reduced porosity in the metal;adhesion onto the substrate; and controlled linear crystalline growth.Therefore, the properties of the deposited metal can be changed withoutheat, pressure, or modifying the system's components or normaldeposition parameters.

The second current, or transverse current, however, is more than a mereimprovement on electroplating or electrodeposition. This is an entirelydifferent current than the first current used to drive metal species tothe surface of the workpiece. The results achieved using the presentelectrochemical methods are impossible with conventional electroplatingor electrodeposition techniques.

Some benefits of the transverse current are illustrated at FIG. 7. Inthis example, the second current 150 is in the form of a bipolar,sinusoidal waveform across a surface 111 of the first electrode 110.Without a transverse current, the electrons 420 are consideredstationary for purposes of this discussion because, while the electronsare in fact moving, their net movement is relatively slow as perEquation 2, as well as non-uniform as a result of electrode resistivityand electrolyte convective field effects. Thus, no relativistic effectis present. The second current 150 effects a relativistic change 112,causing electrons 420 to move across the surface 111 in the directions700A, 700B of the imposed electric field. When the second current(V_(TC)) is positive, electrons 420 accelerate toward the right (700A),and when V_(TC) is negative, electrons accelerate toward the left 700B).This shuffling of the positions of electrons 420 at the surface 111changes the electron distribution, and therefore, the localized chargedensity. When the waveform of V_(TC) approaches 0, electrons may bebunched together or pushed apart farther than normal. In the former, asmooth point 430 on the surface 111 may experience the charge densitynormally seen at points with greater curvature 440. Similarly, thecharge density at curved points 440 may be reduced from their normalvalues.

This change in the electron distribution then alters the behavior ofmetal atoms approaching the surface. Conventionally, the charge densityis greater around irregularities of the workpiece, which then promotelayers of metal to build up the irregularities even more. Instead, inthe disclosed method, atoms are encouraged to follow a path to generatea smooth surface, because areas that would have a large charge densityabsent the transverse current have a lower than typical charge density,and areas with a small charge density absent the transverse current havea greater than typical charge density. The frequency of the transversecurrent's waveform can be swept through several values so irregularitiesof many sizes may be modulated.

The second current may be chosen from an alternating current (AC), or acombination of an AC current and a direct current (DC) offset upon whichthe AC current is imposed. When the second current combines the ACsecond current and the DC second current, the DC second current mayoffset the AC second current by an amount less than an electrochemicalbreakdown of the electrolyte.

When DC is used alone, it moves electrons on the surface of the firstelectrode at a constant velocity, but it does not accelerate them togenerate a relativistic charge at the surface. As shown in FIG. 8A,electrons 420 moving at constant velocity maintain uniform spacing andconstant electric field vectors. A DC offset second current 150 appliedto the first electrode 110 causes a net flow of electrons at a constantvelocity in the bulk and surface of the first electrode 110 inducing amagnetic field at all depths. The bulk fields cancel, while surfacefields propagate outside the conductor. Consequently, a DC offset secondcurrent only weakly impacts the electric field lines 150 from cathodicpolarization of the first electrode 110 under the first circuit 130.

A DC offset (e.g. 0.5 V) keeps the transverse current from beingcentered at zero, so that on the backside of the workpiece, one side ofthe gap would have more deposition and the other side of the gap morecorrosion. Effectively, the DC offset makes one side of the gap act likethe anode more often and the other side of the gap to act like thecathode. The gap will be filled.

With constant velocity electrons, their electric fields are contractedtangential to the surface, and a field intensity increase in theperpendicular directions, following the Liénard generalization:

$\begin{matrix}{\gamma \equiv \frac{1}{\sqrt{1 - \frac{v^{2}}{c^{2}}}}} & ( {{Equation}\mspace{14mu} 1} )\end{matrix}$

where γ is the contraction constant, v is the velocity of the electron,and c is the speed of light (3×10⁸ m/s). Here, the electron velocity isnon-relativistic, so the degree of this effect is small.

When the AC second current is used, however, regular or constant chargeacceleration is induced (FIG. 8B). Under acceleration, electronsexperience a forward compression 810 and rearward expansion 820 of theirelectric field, which propagates outward from the electron's center atthe speed of light. The term “relativistic charge” refers to thisconstant acceleration at or near the speed of light at the surface ofthe first electrode. Before now, electron acceleration and its effectshad not been explored in electrochemical processes. The vector ofacceleration changes with the waveform. That will help further qualifythe last sentence of this paragraph, because electron acceleration

Referring again to FIG. 8A, electric field lines 135 due to cathodicpolarization of the first electrode 110 are normal to the tangentialpoint of the surface 111 due to the symmetry of the electron'selectromagnetic field. When the electron's electromagnetic field is nolonger symmetric due to movement of the charge, the polarization fieldlines are proportionately shifted (137, FIG. 8B). Metals in theelectrolyte (M⁺) flowing to or from the first electrode 110 follow thepaths 135 of these polarization field lines. The field-shifting effectusing the second current 150 may be maintained for periods similar tothe diffusion rates of ionic reactants and the reaction kinetics.

When the workpiece has a void, the second current may have a DC offsetto introduce a potential drop within the void. When two workpieces arenot in electrical contact, the DC offset is applied with considerationto the electrolyte stability. Most electrolytes have a window ofstability around +/−6 V. If the workpieces are in electrical contact,the DC offset can be much greater without damaging the electrolyte,because the current can complete a circuit without depending entirelyupon charge pass through the electrolyte. The electrical contact neednot be within the area targeted for deposition, and the DC offsets canbe much more than +/−6 V, including up to +/−200 V. Gap geometry mayalso affect the limits of the DC offset.

The strength of this electric field, V/m, may be stronger than theelectric field of the first current to reroute metal ions from the firstcurrent into the void. The DC offset may correlate to the voltage atroot-mean-square (V_(RMS)) or the voltage at root-mean-square (I_(RMS)),while the voltage peak-to-peak (Vpp) or the current peak-to-peak (Ipp)may be bipolar. This DC offset leads to transverse growth inside thevoid, and also to the formation of metal-metal bonds within the gap.When the overpotential of deposition is greater, adhesion is oftenimproved. In general, E_(TC) can be much greater than E_(ED), if theworkpieces being joined already have some point of electrical contact.E_(TC) is the electric field of transverse current from the transversecurrent signal source. E_(ED) is the electric field of theelectrodeposition signal source. Greater overpotential can also increasegrain size of the deposition metal, which can harm adhesion, dependingon the system.

The first and second currents may be modulated together so that thepositively biased first electrode continues to experience a positivecurrent efficiency and positive net mass gain (i.e., so the direction ofthe first current does not invert, and the first electrode does notbecome the source of a countercharge). Also, the second current can beseparately modulated so a bottom-up growth occurs inside the void, aphenomenon unknown in conventional electrodeposition without organicadditives (e.g., levelers). See Example 8 for more discussion.

The conductive and dielectric behavior of metal particles in theelectrolyte may affect whether the second current affectselectrophoretic (F_(EP)) or dielectrophoretic (F_(DP)) forces. Forexample, for a 10-μm dielectric particle the electrokinetic field forceimparted can be up to 5 orders of magnitude stronger than that that feltby a conductive particle of the same size. For 10-nm particles, thesituation is reversed. Both are frequency-dependent and particlevelocity may be based on how much energy can be stored in an ionic cloudsurrounding the particle (that is, the “permittivity”). As frequencyincreases into the kHz range, that energy usually decreasessubstantially.

By reducing the stored energy between the metal particle and the firstelectrode, particle riding and occluded porosity are reduced. Withoutwishing to be bound by theory, as the metal particle approaches thesurface of the first electrode, the energy stored in the electrochemicaldouble layer tangentially distributes. E_(TC) competes with E_(ED). Thedouble layer barrier between the metal particle and the surface of thefirst electrode is reduced. The electric field also imparts anelectrokinetic velocity tangential to the surface, which causes parallelwobbling as the particle approaches the surface perpendicularly. Bothmechanisms reduce the porosity of deposits created with particleocclusion following the methods described herein.

F. Waveform

The second current (or induced potential) is a periodic or non-periodicwaveform, such as a sine wave, a triangle wave, a saw tooth, as well asany number of other possible waveform, and combinations thereof. Eachtype of waveform imparts a perturbation to surface charges. Severalwaveforms may also be combined to define the second current. Differentwaveforms have different effects on the surface, even when superimposedas a multi-waveform.

FIG. 9 illustrates examples of the most common fundamental waveforms andtheir properties used in the present method. The waveform and itsvariable parameters (current, voltage, frequency, and duration) may becontrolled to affect the second current. Waveforms induce a potentialacross the surface of the first electrode to move charges across thefirst electrode. Without wishing to be bound by theory, constant voltageover time causes charge to move in a set vector. Charge movement theninduces an electric field between gaps or rough features on a firstelectrode, and induces a magnetic field, H^(→), at the surface of thefirst electrode. Changing voltage over time causes a proportionatelycontinuous acceleration of charges, which induce both magnetic andelectric fields (H^(→),E^(→)) at the surface. A “bump” is an abruptchange in the vector of a charge, such as the apex of a triangle wave(directional bump) or a polarity change (polarity bump). Both appear inFIG. 9 as slews or asymptotic points. “Relative power” describes howdifferent waveforms of identical peak voltage deliver power across theelectrode surface. In electrochemical processes, voltage may be treatedas a constraint instead of a power, because potential isthermodynamically significant to the reaction, while power relates totime and surface area.

The applied waveform may be formed from a combination of numerouswaveforms based on harmonics of one or more frequencies at which theelectrolyte or the first electrode exhibits absorption of the one ormore frequencies. The waveform may include phase offset introduced fromdifferences in potentials between points of contact on the workpiece. Iftwo different sources of electrical contact are used for two separatetransverse current channels, the signals of those channels can bephase-offset, as shown in the 2D simulations. (See Example 8).

Waves go all directions, reflecting and causing peaks in the signal.Non-symmetric reflections result in signal differences, allowing one touse roughness like a fingerprint to uniquely identify a sample. Thewaveform flows through the gap, as an electric field or as a magneticfield. The pattern can become complex. Because of the offset, thecompound difference between the waveforms of the points of contact canamplify the current experienced in the gap beyond the energy. As theroughness changes, the distribution of energy also changes. If theroughness becomes smooth, the distribution of energy across the surfacebecomes more uniform. This change is topography can be measured with areflection or transmission-type impedance.

The phase offset may be between 0° and 180°. With a 0° offset, thecurrent resembles pulse plating. See Example 8 and FIG. 21. At a 45°offset, current density is effected in the gap. The magnitude of theelectric current fluctuates logarithmically. See FIGS. 7 and 8. Thedissolved metal atoms follow the electric field. The magnitude andpolarity result from the differences in the offset. The current density(V/m) increases as the gap closes.

The second current (or induced potential) may also have a phase offsetbetween 0° and 180°, for example a phase offset of about 90° between twoelectrical contacts on the surface. Here, strong vectors are felt at thesurface. Some first current vectors move parallel to the surface,allowing corrosion during deposition. Microscopic analysis of depositedmaterial showed globular pockets of amorphous rather than crystallinedeposition.

At a 135° offset, first current vectors point away from the workpiece,diminishing material deposited and producing a shiny finish. A 180°offset is the largest potential difference possible. The gaps in theworkpiece showed large changes with the field focused on gap filling.See Example 8 and FIG. 22. When the deposited material was rough, theenergy was not presented to the surface in a way that would promotesmooth deposition. Thus, the waveform of the second current was toosimple, and needed to be modulated so that the deposited material issmooth instead of rough. In various embodiments, the second current (orinduced potential) may have a period similar to a diffusion rate of acomponent in the electrolyte.

A power source may apply a waveform as a time-dependent voltage builtfrom the superposition of multiple sinusoidal signals (analogueharmonics). Some waveform generators may increase the number ofharmonics to reduce the magnitude of perturbations in the waveform. Evenwhen V_(peak) is tens of volts, a superimposed perturbation of amicrovolt can affect the second current. A noise signal is composedprimarily of bumps and no repeating periods of constant charge velocityor acceleration. Noise with the same V_(peak) as a sinusoidal waveformwill deliver more electromagnetic radiation (EMR) than the sinusoidalwaveform at 2 Hz. Sinusoidal frequency of a sinusoidal signal, in oneexample, may be 20 Hz at 2 Vpp, or 10 V at 2 Hz, to provide roughly thesame EMR as the 20 Hz signal, without accounting for effects from theradiating body, such as gain and resistance.

When a second current is applied across the first electrode, electronsmove across the surface of the first electrode with a net velocitytoward the electric field. This material-dependent speed, called “driftvelocity,” v_(D), is between about mm/s and about μm/s:

$\begin{matrix}{v_{D} = \frac{I}{n*A*Q}} & ( {{Equation}\mspace{14mu} 2} )\end{matrix}$

where I is current (amperes), n is the volumetric charge carrier densityin the medium (e⁻/m³), A is the area of flux (m²), and Q is the chargeof the carrier (1.6×10⁻¹⁹ C/e⁻). An electron at a constant velocity hasits electric field contracted tangential to the surface of the firstelectrode, and has its field expanded perpendicular to the surface, perthe Liénard generalization. The distortion is negligible if v<<c, as forv_(D).

Therefore, constant electron velocity from second current is limited onthe surface of the first electrode compared to the effects ofacceleration. At frequencies below kHz, impedance can be simplified.Ohm's law determines current flow based upon the voltage/time curves ofa waveform. For a real-world first electrode, v_(D) through the firstelectrode depends heavily upon geometry and, therefore, will benon-uniform across the surface.

Charge produced by electron acceleration propagates across the firstelectrode relativistically, at close to the speed of light, much fasterthan v_(D). Under the AC second current, the average v_(D) is 0, whilethe velocity of propagation is approximately:

$\begin{matrix}{v_{P} = \frac{c}{\sqrt{k}}} & ( {{Equation}\mspace{14mu} 3} )\end{matrix}$

where k is the dielectric constant of the material in the electrolyte.Since charges move on the surface of the first electrode and not withinits bulk, the signal propagation produced by second current moves alongthe first electrode-electrolyte interface. The dielectric constant ofthe electrolyte also affects the velocity of propagation. For example,water has a dielectric constant of 80.4; V_(P) is still 3.35×10⁷ m/s,dramatically faster than mass transport through the electrolyte.

The power of the EMR of a moving particle can be approximated usingLarmor's equation:

$\begin{matrix}{P_{e -} = \frac{\mu_{o}*Q^{2}*a^{2}}{6*\pi*c}} & ( {{Equation}\mspace{14mu} 4} )\end{matrix}$

where μ_(o) is the permeability of free space (4π×10⁻⁷ N/A²) and α isthe charge acceleration, a reasonable approximation when drift speed ismuch slower than the speed of light.

Absent the second current, a charged particle radiates anelectromagnetic field, which dissipates with distance, r, from itscenter as ≥1/r². In contrast, the electromagnetic field of the sameparticle in motion dissipates as about 1/r. Thus, the electromagneticfield of electrons under second current is much stronger, per Coulomb'sLaw:

$\begin{matrix}{{E_{r} = \frac{q}{4*\pi*ɛ_{o}*r^{2}}}{and}} & ( {{Equation}\mspace{14mu} 5A} ) \\{E_{\theta} = {q*\alpha*\frac{\sin (\theta)}{4*\pi*ɛ_{o}*r*c^{2}}}} & ( {{Equation}\mspace{14mu} 5B} )\end{matrix}$

where E_(r) is the electric field radial in all directions to the pointcharge, E_(θ) is the electric field which is perpendicular to E_(r), andε_(o) is the permittivity of free space (8.85×10⁻¹² C²/Nm²). E_(θ) isunique to charges under acceleration and is responsible for the effectsof second current on the electrodeposition. E_(θ) is negligible forcharged particles at non-relativistic velocity and no acceleration.

EMR depends on the acceleration and not the velocity of the electron,and acceleration depends on frequency of the applied waveform. Equallydependent is the power available at the first electrode/electrolyteinterface. The power supplied for sinusoidal second current can bedescribed by:

P _(TC)=½*R _(peak) *|I _(peak)|² =P _(rad) +P _(ohm)  (Equation 6)

where R_(peak) and I_(peak) are the peak resistance and current of thewaveform, respectively. P_(TC) can be divided into radiated power(P_(rad)) and power dissipated due to ohmic losses (P_(ohm)).

AC second current increases bulk resistance and channels more power tothe surface of the first electrode where the resistance is less. Thisphenomenon is called the “skin effect”:

$\begin{matrix}{S_{D} = \sqrt{\frac{1}{\pi*f*\mu*\sigma}}} & ( {{Equation}\mspace{14mu} 7} )\end{matrix}$

where f is the frequency, μ is the permeability of the electrode, and σis its conductivity. S_(D) describes the approximate depth from thesurface of the first electrode, at which P_(D)=P_(TC)/e. The AC secondcurrent, especially at higher frequencies above 1 GHz, more efficientlyuses the second current power.

The roughness may exceed the calculated skin depth at ≥1 MHzfrequencies. The result of such roughness is a change in the vector ofv_(D) on the first electrode and an attenuation of the EMR travelingaccording to v_(P):

$\begin{matrix}{Y_{RMS} = {Y*( {1 + {( \frac{2}{\pi} )*{\tan^{- 1}( {{1.4}*( \frac{R_{RMS}}{S_{D}} )^{2}} )}}} )}} & ( {{Equation}\mspace{14mu} 8} )\end{matrix}$

where Y_(RMS) is the modified attenuation constant of the electrode dueto roughness, Y is the original attenuation constant of the material,and R_(RMS) is the RMS roughness. This relationship under Hammerstadmodel demonstrates increased attenuation from roughness by unity for thesmoothest surfaces and by double for the roughest surfaces. Powerdissipation results from micro-field formation between roughnessfeatures, and can be absorbed by interfacial electrochemical processes.See also Example 9. With the appropriate waveform, fields from thesecond current affect the first, secondary, and tertiary electric fieldsat curvature. The secondary and tertiary electric field cause convectivecharge transfers. The frequency of the second current may be determinedbased upon the skin depth of the applied power. Generally, thetransverse current causes a more uniform micro-current and macro-currentdistribution.

EMR occurs at the first electrode/electrolyte interface per P_(e−) andradiates away from the surface per v_(P). The energy from 0 to somedistance, R_(NF), from the interface is both radiative and reactive:

$\begin{matrix}{R_{NF} \leq {{0.6}2*\sqrt{\frac{D^{3}}{\lambda_{TC}}}}} & ( {{Equation}\mspace{14mu} 9} )\end{matrix}$

where D is the maximum dimension of the electrochemically active firstelectrode or the distance between the electrodes applying secondcurrent, and λ_(TC) is the wavelength of the second current. This regionis the reactive near field and within it, E_(θ) and E_(r) are in-phasewith the magnetic field of the EMR. As energy interchanges between E^(→)and H^(Θ) every quarter period, the electric fields exhibit capacitivebehavior, while the magnetic field exhibits inductive behavior. Withinthe near field region, electrochemical polarization field lines and anyionic species in the electrolyte reacting with them are subject to thesefrequency-dependent capacitive and inductive fields.

Another consideration is that the waveform period determines the slewrate and, therefore, the potency of 10 μVpp compared to 10 Vpp (FIG. 9).Without wishing to be bound by theory, the effect of the electric fieldinduced by second current over an area may depend upon the gradient ofthe field over the area, or the “slew rate,” ΔV/Δx. (x may be the spaceor time domain.) Although their peak magnitudes perpendicular to thesurface are never the same, a high potential, low frequency waveform mayhave the same slew rate as a low potential, high frequency waveform atcertain points or times, particularly at a bipolar bump. At highfrequencies even sinusoidal features may appear asymptotic.

Phase-offset is another controlled variable, which could tune the effectof the second current across the first electrode. For example, twoequal, sinusoidal waves phase-offset by 170°-180° mostly cancel eachother throughout the signal-generating circuit. The second current poweris stronger at rough and/or asymmetrical areas due to less cancellation,having a localized effect on simultaneously occurring electrodeposition.Once deposited material has filled in the abrasion and restored symmetryto the first electrode, the second current power self-cancels. Ifcancellation increases substantially before surface imperfections havebeen removed, a larger phase offset may be applied. A benefit of usingsuperimposed signal cancellation reduces the far-field radiating powerfrom the first electrode, compared to a single second current with largepower and a complex waveform.

Each component of the devices described herein facilitates chargetransfer at different rates. If the AC frequency is too fast, slowerprocesses may be unaffected. Likewise, slower AC frequency does notaffect processes which occur over drastically faster periods. Secondcurrent frequencies of about Hz and about kHz can affect ionicdisplacement reactions, such as ionic reactants in the electrolyte.Faster frequencies may alter the cathodic polarization field lines atabout the v_(P), but the reactants move too slowly to respond to thosechanges simultaneously and will instead respond with some probability,similar to aliasing within telecommunications and computing. Frequenciesbetween about kHz and about MHz are timed to the rotational moment ofpolar molecules. Above about 100 MHz, many aqueous electrolytes cease toconduct and instead behave capacitively. Arbitrary waveforms, such assuperimposing a high frequency waveform over a lower one, balance theseeffects. Such waveforms can be defined by variables modified during anelectrochemical process in response to changes in the system (feedbackloop). For example, an adequately enabled oscilloscope may monitor thesecond current to observe phenomena or gradual changes during anelectrochemical process to troubleshoot, refine signals, or give sensoryfeedback (phase shift, attenuation, etc.).

G. Applications of the Method

The methods described herein may be applied to many electrochemical,metal deposition, and metal bonding applications, including corrosion,electropolishing, and the electrochemical processes within batteries.

1. Corrosion Processes

Most corrosion processes are an unintentional consequence of amaterial's reactivity with its immediate environment. Boats, oil rigs,and other vessels regularly exposed to saltwater constantly corrode dueto localized potential differences. Metals contacting otherelectrolytes, such as metal tanks storing strong acids, or metal pipescontaining mineral-rich water. The metal slowly corrodes into theelectrolyte, leading to electrolyte contamination, and structuraldeterioration of the metal component. Steel frame buildings, ships, oilrigs, tanks, pipes, and other structures with large dimensional aspectratios can experience an induced potential drop across the surface fromelectrolyte flow. Potential differences between the metal andelectrolyte and potential differences between adjacent metals (Cu, Zn,and Fe) are present regardless of electrolyte movement.

To avoid unwanted corrosion, a negative potential is sometimes appliedto the entire structure to maintain the structure at a DC electricalpotential below the corrosion potential. This method is referred to as“impressed current cathodic protection”, or “ICCP.” While ICCP reducescorrosion, its effectiveness is limited by the placement of nearbyanodes. The overall effectiveness of ICCP could be enhanced by a methodthat better distributed charge across a vulnerable surface.Alternatively, in situations when anodes cannot be placed appropriately,a transverse current can be more effective.

By using a method described herein, a second current may reducecorrosion at a junction between two or more galvanically reactive metals(such as Cu wire on Zn-coated Fe in saltwater). No first (deposition)current is used in this example. Under these conditions, the secondcurrent can distribute the charge away from grain boundaries on thesurface of the first electrode, avoiding corrosive pitting at thatsurface. See also Example 7.

With few exceptions, linear corrosion, the predictably slow andrelatively even loss of material across a surface, is much less aboutthan the accelerated corrosion that occurs in isolated areas due topitting. The protective properties of any coating are circumvented by asingle chink in the armor: Pitting begins at a compromised point in thecoating and metal corrodes out from underneath the surrounding intactcoating through this single access. As the surface area of the pitgrows, the corrosion rate increases and, instead of a slow and evenloss, a structurally compromised area is rapidly created.Electrochemical countermeasures do not avoid this process and insteadsuppress linear corrosion by decreasing the surface voltage at aprotected area below the voltage of corrosion. However, the powerrequirements and effectiveness can vary significantly with fluctuationsin the surrounding environment.

Due to these limitations, self-healing coatings that prevent even singlechinks are a critical area of development regardless of a coating'sother properties. Yet in their chemical formulation the two cannot beseparated and effective solutions are inherently case by case and slowto develop. The disclosed process can be deployed with or withoutsurface coatings or conventional electrochemical anti-corrosion systemsas necessary to dramatically suppress pitting and suppress the mostcostly forms of corrosion.

2. Electropolishing

Conventional electropolishing is a type of corrosion process in which apositive potential is applied to a surface to corrode away roughfeatures and render a smoother surface. Advantageously, rough areascorrode faster than smooth. Because conventional electroplating producesunwanted roughness, electropolishing is often used after conventionalelectroplating to remove accumulated roughness and provide a smoothfinish. Electropolishing current densities are usually low and/orpulsed. This maintains a smooth finish at the expense of overall processtime. When higher current density is applied, corrosion occurs morerapidly along grain boundaries of the metal, causing chunks of metal todetach from the bulk of the surface and increasing surface roughness.

Instead of allowing unwanted roughness to accumulate in a conventionalelectroplating process, roughness can be addressed directly with awell-calculated waveform produced for evenness in the z-direction whileoscillating the y-direction, or with an AC component using the methodsdisclosed herein. The goal is to maintain oscillation in the y-directionwhile controlling or minimizing fluctuations in the z-direction byswinging and changing the magnitude of the vectors. In this way, aflattening of surface features is promoted without vertically buildingfeatures, as seen in conventional processes. The deposition current ismodulated relative to the transverse current to ensure the overallelectric field strength relative to the workpiece surface is constant,while the parallel field strength may wander. The first and secondcurrents may be coordinated together so weak and strong fieldcomplement. The deposition and transverse currents may pass through thesame electrical junction. The total electrode signal may look like pulseplating, but that does not account for the different signals put intothe workpiece to generate the disclosed effect. See Example 9.

By using a method described herein, the second current betterdistributes current. Higher current densities may be run while avoidingthe surface corrosion in chunks and along grain boundaries.Electropolishing yields a nearly smooth surface by corroding away theedges and rough features without the spalling seen in prior art methods.A DC field may be applied in the opposite direction of the electricfield needed to promote electrodeposition In other words, if the DCfield that promotes deposition is negatively polarized relative to theworkpiece, then reversing the polarity of that DC field promotescorrosion, thus electropolishing the workpiece. With the methodsdisclosed herein, electropolishing may be accelerated.

The backside of the workpiece may also be electropolished without a DCoffset. A set of deposition electrodes may be arranged on the backsideof the workpiece. In a conventional electrodeposition, most of the metalis laid down on the edges facing the void space of the gap. The thinnestamount of material is deposited in the center of the gap, resulting is apoor junction Using the disclosed process, the opposite effect prevails,where corrosion is preferred at the edges but deposition is preferred inthe gap. Metal fills in the entire void space.

3. Batteries

Also provided herein are methods for charging an electrochemical cell,such as a battery. These methods suppress and reverse dendritic growth,a common source of failure for most batteries.

Batteries generally comprise repeating units of sources of acountercharge and first electrode layers separated by an ionicallyconductive barrier, often a liquid or polymer membrane saturated with anelectrolyte. These layers are made to be thin so multiple units canoccupy the volume of a battery, increasing the available power of thebattery with each stacked unit. As these components become thinner, theyalso become more fragile. Further, as the electrodes become thinner, alarger ohmic drop occurs across the surface leading to less uniformcharge density during charge/discharge cycles.

For example, lithium batteries typically have a metal oxide electrode (Mis typically iron, cobalt, manganese), and a carbon electrode coated onmetal current collectors. The metal oxide is added to stabilize thelithium metal. The metal oxide electrode starts as M_(x)O_(y) and thecarbon starts as atomic Li-infused graphite. During discharging (thatis, normal use of the battery to provide power to a device), the Li⁺ions travel from the carbon through the membrane and intercalate intothe MA to become LiM_(x)O_(y). During charging, the Li⁺ ions follow theopposite path and instead intercalate into the carbon. Under idealconditions, every Li⁺ ion finds a vacant Fe_(x)O_(y) site or carbonsite, and not sites where another Li⁺ ion has already been absorbed.Problems arise if the Li⁺ ions try to deposit atop more Li⁺ and 3Ddeposits of Li⁰ form. Li⁰ aggregation creates an explosion hazard andcauses roughness. Specifically, if the Li⁰ reaches the oppositeelectrode, the battery may short and the dendrites formed during the Li⁰deposition may damage the membrane dividing the two half-cells of thebattery.

With subsequent charge/discharge cycles the lithium deposits withincreased roughness. Lithium-metal batteries (Li-foil anode) andlithium-ion batteries (Li-ions intercalated into a graphite/foil anode,where the foil is frequently copper) both suffer from the growth oflithium dendrites during the battery's charging cycles. While Li-ionanodes can be stable for hundreds of cycles, dendrites developimmediately in Li-metal. Once formed, the dendrites lower the columbicefficiency of the battery, damage the ion membrane, and short thebattery if the dendrites contact the anode. Commonly dendrites formwhich puncture or irreversibly damage the electrolyte membrane. Ifdendritic growth reaches the opposing electrode, then the battery ispermanently shorted and cannot be recovered.

Both types of lithium ion battery form a solid electrolyte interphase atthe interface of the anode and electrolyte as the lithium chemicallyreacts with the electrolyte. The interphase is a layer comprising theinsoluble reaction products which collect at the interface. Li ions mustpass through the interphase from the anode. Because the interphasegenerally has a higher impedance, non-uniformity of the solidelectrolyte interphase across the anode can cause uneven currentdistribution across the anode. This unevenness encourages channels toform through the interphase where Li concentration is high. Thesechannels lead the formation of dendrites. Transverse current can enforcea uniform current distribution across the entire surface, more evenlydistribute Li concentrations throughout the solid electrolyteinterphase, and maintain an anode/electrolyte interface with uniformelectrical behavior.

Although this discussion exemplifies lithium-ion batteries(lithium-impregnated into graphite), the methods disclosed herein applyequally to other battery types, including lithium metal batteries andlead acid batteries. Pure lithium metal has a much higher (˜5×) energycapacity, but there is no teaching in the art of how to control dendritegrowth. These batteries typically last only ten charge-discharge cycles.Failure is instantaneous and more severe than the widely usedlithium-ion batteries. The methods described herein control dendritegrowth in lithium metal batteries, making these batteries practical andopening the market to batteries with an energy density superior tolithium ion batteries. The method would run every time charge cycle tostymie the formation of dendrites. The electrolytes are selected toallow even deposition of lithium metal during healing process onrecharge.

Regarding lead-acid batteries, the methods described herein are modifiedto account for the configuration of the electrochemical cell and itselectrochemistry. Unlike a lithium-based battery, both the anode and thecathode must be recharged. Existing cells have only two ports, so thetransverse current must be sent in one port calculated to reflect offthe far wall of the cell and back to the port of entry. The waveform ofthe transverse current would be swept through several frequencies toresonate with dendrites of different sizes on the anode and cathode ofthe lead acid battery.

As batteries become smaller with increased power capacity these issueshave been amplified and pose significant design constraints. Thelifetime and performance of batteries with lithium or any otherchemistry can be greatly prolonged by increasing the smoothness anduniformity of metal charge carrier species during dissolution anddeposition. And the rate of recharge could be increased withoutcompromising the lifetime of the battery as with conventional batteries.

The methods as described herein provide a means of increasing chargehomogeneity on electrodes with significant ohmic drop. This reducesthermal gradients and hot spots, which would otherwise cause exothermicbattery failure. Further, this would reduce the performance deviationsamong individual batteries in a stack that occurs as batteriesindividually age and degrade at different rates. This configuration isdifferent for every battery system type.

II. Device

The present disclosure also provides a device for performing the methodsdescribed herein. As shown in FIG. 1A and others, the device 100comprises a source of a countercharge 120 and a first electrode (e.g.,workpiece) 110—although the workpiece is a temporary part of the device.The source of countercharge 120 and the first electrode are 100 inelectrical communication through an electrolyte 140. The device 1000includes a current generation source, such as power supply 160, toinduce a first current 130 between the source of a countercharge 120 andthe first electrode 110 through the electrolyte 140. The current sourceincludes a connection to the source of a countercharge 120 and the firstelectrode 110. The current source, or another source, also is connectedto the electrode to induce a second current 150, sometimes referred toherein as a “transverse” current, across the first electrode. The secondcurrent 150 is transverse or otherwise across the first current 130 atthe first electrode 110. The second current 150 is controlled to inducea relativistic charge across the first electrode.

Referring now to FIG. 10, the present disclosure further provides adevice 1000 having a main control unit (MCU) 1020 and an electrodeapplicator unit 1010. The MCU 1020 contains a power supply 160 and apower modulator 165, which induce a first current 130 between the sourceof a countercharge 120 and the first electrode 110 through theelectrolyte 140. The MCU 1020 also supplies power to induce a secondcurrent 150 through a surface 111 of the workpiece 110. The electrodeapplicator unit 1010 contains at least one source of a countercharge 120and a plurality of channels 145 for flowing an electrolyte 140 throughthe electrode applicator unit 1010. The electrode applicator unit 1010is connected to the main control unit 1020 through a current collectorcable 161 connected to the main control unit 1020 and a power controlunit 1030 connected to the main control unit 1020. The power controlunit 1030 applies a first current 130 between a first electrode 110 andthe at least one source of a countercharge 120 through the electrolyte140. The power control unit 1030 may also induce a second current 150across the first electrode 110. As described elsewhere herein, thesecond current 150 is transverse to the first current 130, and may becontrolled to induce a relativistic charge across the first electrode110.

The electrolyte 140 need not be contained within a bonding system 1000.The electrolyte 140 may act as a linear resistor. The father the sourceof countercharge 120 is held from the surface 111 of the workpiece 110,the more resistance passing charge through the electrolyte 140, and theless current density at the workpiece 110. In other instances, theprocess may be run through a controlled current mode at the powercontrol unit 1030, in which the bonding system 1000 increases thevoltage to maintain the selected current density at the surface 111 ofthe workpiece 100 when the applicator 1010 is moved.

For a bonding system, one or more applicators 1010 supply new materialand supply current to the first electrode, as shown generally at FIG.10, and in various alternative embodiments at FIGS. 11-13. Theapplicator 1010 may comprise several contacts for the first current 130and the second current 150, channels 145 for fluid flow of theelectrolyte 140 through the body of the applicator 1010, and auxiliaryelectrical components. The applicator 1010 may have an integratedheating 146 and/or cooling unit 147, or more generally a temperaturecontrol unit, which control the temperature of the electrolyte 140within. The applicator 1010 and the MCU 1020 may be connected by wiring161 for power and sensors, and tubing 169 that allows fluid to flow fromone to the other.

The device 1000 may further comprise a current collector cable 161connected to the MCU 1020 via wiring, with leads for attaching to thefirst electrode. Under operating conditions, the substrate 110 becomesthe working electrode.

The device 1000 may further comprise a power control unit 1100, whichsupplies power for the first current 130 and the second current 150.

The devices may use any electrolyte described herein. The electrolyte140 may be stored in a tank 167 or other form of container, which may beintegrated or removable. When present, the tank 167 supplies theelectrolyte 140 to the applicator 1010. A pump 168, depending theconfiguration, may be positioned to drive or otherwise pump electrolyte140 from the tank 167 through the tubing 169 to circulate electrolyte140 for distribution on the workpiece where desired. In such aconfiguration, the electrolyte 140 may be dispensed through theapplicator 1010.

A. Main Control Unit

Referring to FIG. 10, the main control unit (MCU) 1020 may house a powersupply 160, a processor or other compute components in communicationwith a memory or other tangible storage medium including software 164forming executable instructions or control sequences, acomputer-controlled power modulator 165, and auxiliary electronics 166.In the main control unit 1020, the processor 164 is configured toexecute the instructions stored on the computer readable medium. Thepower modulator 165 and the power supply 160 may be controlled by theprocessor 164.

The MCU 1020 may include one or more additional electrical components,such as a first control system, power generation subsystem fordeposition/corrosion, power generation subsystem for the second current,and sensor-based feedback subsystems. When present, the first controlsystem accepts user input for the chemistry and operating conditions andto control the subsystems to provide power for first and secondcurrents. The first control system may be digital for complex systems,or analogue for simple systems with fewer chemistry requirements.Computer control may be used for the broadest range of materials,sensory feedback, data recording, and complex deposition conditions.

The deposition power subsystem must have stable mA and mV control withlow internal reflection. The subsystem may provide DC and AC powerbetween about 1 Hz and about 1 kHz. The subsystem may be programmable toapply voltages relative to sensor input from a sensor subsystem. Thecurrent may range between about 0 mA/cm² and about 200 mA/cm² perchannel relative to the area of the first electrode for an application.The current may also range between about 0 mA/cm² and about 300 mA/cm²per channel relative to the area of the first electrode for anapplication. Multiple channels and/or fast switching may be used whenneeded, such as when joining two portions of a first electrode, or whenthe MCU 1020 controls bonding at multiple areas.

The deposition power subsystem may apply power with modulated firstcurrent. Current-controlled power may achieve a current density (A/cm²),and so a desired mass flux from metal of the electrolyte onto thesurface of the first electrode. Potential-controlled power may achieve aredox state of substrate atoms at the first electrode/electrolyteinterface. For example, a slightly negative potential could be appliedto the first electrode to ensure a metallic state of the surface atomsand to prepare the surface for adhesion. Potential control of positivepolarity at the first electrode may corrode the surface of the firstelectrode. For example, the MCU 1020 could effect a potential equal toor greater than 0.8 V but below 1.6 V vs. a standard hydrogen electrode(SHE) to corrode a steel surface without corrosively pitting. This wouldbe useful for increasing the penetration depth of deposited layers onthe surface of the first electrode without causing significantroughening. Potential control may also control the stoichiometry ofdeposited alloys or composites via potentials of the first current ofbased on the metal from the electrolyte.

For example, in an ionic liquid electrolyte containing both Fe and Mnspecies, the MCU could effect a potential of −0.3 V vs. Fe/Fe⁺ for 2 sfollowed by −0.9 V vs. Fe/Fe⁺ for 2 s. The first potential surpasses theactivation energy for Fe to deposit, but is insufficient to drive Mndeposition. The second potential exceeds the activation energy of Mn⁰formation and so both species electrodeposit simultaneously. Theoverpotential (that is, the potential applied in excess of theactivation energy) impacts the relative deposition rate of each species.Other alloys may be used by changing the metal species and selecting theappropriate voltage, as taught herein. See the FeZn alloy at Example 13.

The MCU 1020 can apply DC or AC and obtain feedback measurements whichallow the computer to modulate outputs. For example, the power controlunit (PCU) 1030 might operate in a DC mode to measure the open circuitpotential (OCP) between the first electrode 110 and source of acountercharge 120 so potentials may be applied relative to the OCP. TheMCU 1020 can also use DC current to measure dynamic capacitance of theelectrochemical double layer at the surface of the first electrode.Because the double layer capacitance may proportionately indicatechanges in the surface area 111 of the first electrode 110 duringoperation, such a reading may allow the MCU 1020 to alter the secondcurrent 150 or to maintain the current density (A/cm²) specified as newmaterial is added to the first electrode 110. AC can be applied by theMCU 1020 to obtain resistance/impedance measurements. For example, theMCU 1020 can rapidly apply an AC of 1-100 mV and a frequency less thanor about 100 kHz to measure the linear impedance response and obtainfeedback about the bulk conductivity of the first circuit. If areference electrode 148 is present in the applicator 1020, additionallower frequencies can monitor the first electrode/electrolyte interface.

The MCU 1020 may periodically interject these modifications into adeposition sequence to obtain feedback. The computer 164 may comparethis feedback to models and user-specified operating parameters tomodulate the applied power driving deposition and second current.

For example, after 1,000 corrosion/deposition pulse iterations (or everyseveral seconds), the MCU 1020 may superimpose a 10-mV, 500-kHzsinusoidal AC wave onto the DC potential of the preceding pulse of thefirst current 130 to measure system impedance. The measurement timewould depend on the frequency and the number of wave periods recordedand the processing time for the computer to analyze the recorded signalagainst the applied waveform (˜10-50 μs total). If impedance hasincreased relative to the last data point collected, the computer 164may determine whether this increase correlates with an expected gradualloss in ionic conductivity of the electrolyte with use and time. If so,the current/potential magnitude of later pulses may be increased toovercome the additional ionic resistance of the electrolyte 140. Theentire sequence may be repeated using updated parameters. If not, thenthe MCU 1020 measures impedance/capacitance at one or two lowerfrequencies to probe the condition of the surface. And immediately afterthe user turns on the power, and again immediately after power is turnedoff, the MCU 1020 may measure the OCP of the system to estimate theredox state of the first electrode surface 111.

When present the second current power subsystem may have multiplechannels with variable output impedance, wideband frequency range(0-GHz), DC offset capability, and waveform generation. Internalamplification and attenuation enables an MCU for larger work areas andmay apply μV or smaller perturbations. Separate channels may modulatetheir output signal relative to one another.

Sensor power subsystems, when present, may allow for processing offeedback/feedforward from electrodes for parameters such as reference,pH, conductivity, signal impedance and attenuation, and whether or notan electrode is contacting the surface of the first electrode. They mustalso process feedback from temperature sensors and provide power for tipchamber heating when needed. These systems provide feedback to the firstcontrol system so it can modulate deposition and second currentcircuits.

The MCU 1020 may have an onboard interface, or connect to externalcomputers for programming through separate software. Any devicedescribed herein may also further comprise a signal canceler to reduce afar-field radiation from the first electrode.

B. Applicator

Referring now to FIGS. 10-13, many designs can be used for the electrodeapplicator unit 1010 (FIG. 10), including a gun-type applicator (FIG.11), a patch-type applicator 1200 (FIG. 12), or a glove-type applicator1300 (FIG. 13). Generally, the applicator 1010 may comprise at least oneionic contact with the first electrode 110 via a complete circuit 130between the source of a countercharge 120 and electrolyte 140. Manyvariations are envisioned within this general design, including, but notlimited to, one or more points of electrical (non-ionic) contact, suchas two or more points of contract, with the first electrode 110 inspatial proximity to the point of electrical contact, a reservoir 167 ofenough volume to contain and dispense electrolyte, a corrodingelectrode, a source of a countercharge 120, a reference electrode (RE)148, and a longitudinal receiving antenna that would allow for z-axisamplitude electromagnetic inputs and feedback modifications for thesecond current 150 applied for smoothing or resolution of otherstructural abnormalities resulting from the process. Other process mayuse one point of contact, especially a high frequencies.

Gun or wand applicators may have an application system similar to thatshown in a representative section view at FIG. 11A and a top view atFIG. 11B. The base 1110 of the applicator 1100 may have a feedthroughfor a corroding electrode, or a seat for an interchangeablenon-corroding source of a countercharge 1120. Any corroding electrodedescribed here may be used. The seal electrically polarizes the firstelectrode. The seal defined one point of contact so far as the circuitis concerned, even though the geometry of the contact encloses a largearea. The base 1100 may also have an electrode 1130 separate from 1120.Electrode 1130 may be a parallel source of a countercharge to modify orstabilize the total first current without changing the potential throughthe source of a countercharge 1120. In this way co-deposition may becontrolled independently of the overall deposition process.

If a reverse pulse deposition process or corrosion of the firstelectrode is chosen, then electrode 1130 may be a cathode so reductionon the source for a countercharge 1120 is not mandatory. Electrode 1130may instead be a reference electrode (e.g. 148 in FIG. 10), or aseparate reference electrode may be placed in a similar location on theapplicator 1100. Electrode 1130 may be a single surface, or multiplesurfaces with directional control. Electrolyte may be circulated throughthe system via one or multiple, opposing channels 1140, 1145. Theapplicator 1100 may contain one or more channels 1150, 1155 for freshand depleted electrolyte.

The applicator 1100 may contain two sources of countercharge 1120, whichcontact the first electrode via the tip 1160, inducing a second currentacross the first electrode. The sources of countercharge 1120electrically contact the first electrode through caps 1170, 1175. Thecaps 1170, 1175 may comprise carbon or soft metal pads, or harder metalpins when it is desirable to increase localized current density of thesecond current.

Flow and electrode geometry inside the applicator 1100 may betwo-dimensionally symmetric. Alternatively, the flow pattern may includea electrolyte influx down the center of the applicator, to the tip 1160,followed by outflux along the outer perimeter of the applicator 1100.

The interchangeable tip 1160 provides space for the electrolyte. The tip1160 may have a sealing material around its opening to isolate theelectrolyte from the channels 1150, 1155 when in contact with a surface.The channels 1150, 1155 may be used with or without separate leadsidentically polarized and connected to the first electrode. The caps1170, 1175 may isolate the electrolyte from oxygen and moisture.

The tip 1160 of a gun or wand applicator 1100 may be fixed or removable.Primarily, the area and geometry of the opening of the tip 1160 woulddetermine the surface area of the first electrode contacted, andtherefore the area onto which new material is electrodeposited.Secondarily, the area and geometry of the tip 1160 may exploit surfacetension of the electrolyte to influence fluid from draining from theaperture when the tip volume is full. The tip 1660 or applicator 1100body may contain an agitator for the electrolyte, including higherfrequency ultrasonic transducers, low frequency vibrators, or anyrelated mechanism. The tip may be designed for directional use. Ascoop-like tip may use sheering force of the first electrode surface topush electrolyte back into the applicator as the tip is guided acrossthe surface of the first electrode.

The base or tip may house a chemically resistant thermocouple or thermalresistor (thermistor) to monitor heat flux near the surface of the firstelectrode. The tip may be constructed of a semi-flexible material tofacilitate consistent contact against non-planar surfaces and to providea seal against excess electrolyte leaving the boundary of the tipopening. Fluid behavior at this junction may also be controlled byselecting the viscosity of the electrolyte and the diameter of the tipaperture to constrain the electrolyte.

The tip may contain a dielectric mesh, which contacts the surface of thefirst electrode to distribute the second current by minimizing energyabsorption by the electrolyte at hot spots. The dielectric mesh may be ametal mesh, a metal mesh in a polymer, or a dielectric polymer mesh.When present, a metal inner later provides a conductive surface forcapacitive coupling of the radio frequency originating from theworkpiece. The metal inner layer is also an effective ground plane,while the polymer outer layer protects the metal inner layer fromdepositing or corroding.

When present, the mesh may be have a porosity between about 1 mm andabout 1 μm, to avoid any slowing of mass transport between theelectrolyte and the surface of the first electrode. The mesh may alsohave openings, such as a slits can be oriented over a junction or gap inthe first electrodes. The material of the source for a countercharge mayclosely match the material composition of the first electrode.

Referring to FIGS. 10 and 11, the tip 1160 may contain a referenceelectrode (RE) 148 of the 1^(st) or 2^(nd) kind. Short, single datapoint feedback measurements using the RE may use an RE of the 1^(st)kind (RE1) may comprise noble metals, Pt, Pd, Au, Ag, or others. Withthese reference electrodes, fast potential measurements may be recordedwhile the surface state of the RE is relatively stable. Polarization ofthe RE over longer time domains would allow the measured feedbackpotential to drift as the RE1 surface conditions become more transient.To obtain feedback over longer periods, an RE2 should maintain asteady-state potential while continuously polarized in solution. Anexample RE2 would be Ag/AgCl.

With a patch-type applicator 1200, referring to FIGS. 10, 12A and 12B,new metal deposition can be achieved by adhering the patch 1200 over thearea of the first electrode 110 to which new metal will be deposited.The patch may have an adhesive or magnetic area 1210 by which to attachto a first electrode 110. At the center of the patch may be an inset,electrochemically active area 1220, composed of a conductive back layer,such as a metal foil. In various embodiments, this back layer may be acorroding or non-corroding electrode, which provides a source of acountercharge 120. The remaining volume of the inset may be filled withelectrolyte 140. The electrolyte 140 may be of high viscosity, such as agel, or be of low viscosity within a sponge or porous membrane. Anyelectrolyte described herein may be used. The perimeter of active area1220 may have a contiguous seal made of silicone, latex, or similarmaterial. This seal, when present, may isolate the electrolyte 140 fromauxiliary contact pads 1230, 1235, which provide electrical contact withthe first electrode 110.

Two contacts pads 1230, 1235 are shown at FIGS. 12A and 12B, more may beused in any orientation around the active area 1220. The pads 1230, 1235provide first current 130 to the electrochemically active area 1220 ofthe first electrode 110 and second current 150 across the area oftreatment. The patch 1200 may be as long as desired or of any geometryso the electrochemical process can occur over a larger area at one time.Power may be provided to the patch through a cable 1240, which may leadto a power supply/control unit 1030, or the patch 1200 may be powered byan onboard battery and simple control circuit. Leads 1241, 1242 connectthe cable 1240 to pads 1230, 1235. A single electrical contact pointtouching the surface may also be used.

Referring now to FIG. 13, the applicator 1300 may be integrated into awearable glove 1310, permitting tactile sensory feedback with manualarticulation. Corroding or non-corroding source of a countercharges maybe seated into the first electrode holder 1320, or the entire tip of thedigit may provide a source of a countercharge. Similar sources ofcountercharge 1330, 1335 may be on the tips of the nearest digits. Thefirst circuit is completed between the first electrode holder 1320, thefirst electrode, and the sources of countercharge 1330, 1335, while thesecond circuit is completed through the sources of countercharge 1330,1335 and the first electrode. Each circuit may be powered by wires 1340,1342, 1343 leading to a junction or gap 1350, which is connected to awire 1360 leading to a power supply/control unit, or an onboardbattery/control system. The user can articulate the first electrodeholder 1320 to control the area of deposition while changing therelative positions of the sources of countercharge 1330, 1335 to controlthe vector of second current. Other digits or multiple gloves may beused.

In the configurations, the applicator 1010 may further comprise aheating unit 146 or a cooling unit 147. Theses unites 146,147 modulatethe temperatures of the electrolyte 130 within the channels 145 of theelectrode applicator unit 1010.

III. Software

The present disclosure further encompasses software for operatingdevices described herein and for performing methods described herein.

For example, the MCU may be programmed to use common materials such assteel, Cu, Ni and Zn with the appropriate electrolyte for each material.The MCU may be modified with enhanced programming to modulate theefficient electrodeposition of more complex alloys and composites.

The MCU may have wired or wireless networking or computer-linkingconnectivity. These connections may load sensor data logs to a computerreadable medium. The connections may facilitate computer control duringoperation of the method, live remote monitoring, and communicationbetween multiple MCUs. The connections may receive software updates,including operating parameters and models for different substratematerials and electrolytes. For example, party A may create aelectrolyte with special operating parameters and create a computermodel that can be loaded onto the MCUs for other users.

The software may allow the MCU to control the deposition and secondcurrent functions during operation within minimal input from the user.Parameters may be initially entered into the MCU, or changingperiodically to refine the process, so user feedback during operating islargely limited to starting and stopping the process.

IV. Metal Deposits

The present disclosure also provides amorphous metal deposits formed byelectrodeposition. The metal deposits may also exhibit one crystal planemore often than other crystal planes

An adlayer may be deposited onto the workpiece to promote adhesion forthe metal deposit. “Adatoms” have not given up all the electrons forform a full bond. Rather, the atoms slide around until they hit newlayers, promoting layer-by-layer growth. The methods described hereinare not just top-down deposition of new material but promoteself-leveling atoms.

Grain size may be modulated by selecting deposition speed. Generally, aslower deposition results in larger grain sizes and a faster depositionin smaller grain sizes. A gradient may also be imposed across theworkpiece so that the deposition in one region is thicker and is at theother end of the gradient the deposition is thinner.

The present disclosure also provides methods for plating on thesemi-conductive and non-conductive workpieces, such as carbon-fiberweave and Kevlar™ fabric. Carbon-fiber is minimally conductive, but canbe directly metallized with the methods described herein. Other fabrics,such as Kevlar™, may be treated before metallization by impregnatingwith metal ions. Any woven material is suitable. For example, a cottoncloth may be impregnated with NiCl₂ overnight. Fabrics may be straight,stiff, and/or distribute stress forces. Generally, metallizationreplaces conventional epoxy treatment.

For example, a bike may use a carbon fiber frame metallized withaluminum. Flex may be defined in the frame. The shape of the carbonfiber enables a range shapes and weight load distributions.

In another example, body armor may be formed from one or more metalizedlayers of a paraphenylene terephthalamide (para-aramid) fiber, such asDupont™ Kevlar®. Conventional body armor requires instead of theconventional 7 to 9 layers of Kevlar® to meet ballistics requirements.Even while accounting for the added weight of the metallization, the newbody armor is thinner and lighter, allowing longer durations ofcomfortable wear. To armor vehicles, the Kevlar® may be shaped intopanels and metalized to form the body of the vehicle. Again, like bodyarmor, the vehicle paneling is thinner and lighter while providingequivalent protection from projectiles and other weapons.

EXAMPLES

The following symbols and abbreviations are used throughout the presentdisclosure:

-   ∂Average diffusion layer thickness of reactive species in    electrolyte-   A Area of flux (m²)-   AC Alternating current-   c Speed of light (3×10⁸ m/s)-   CA Corroding Source of a countercharge-   D Longest EMR-active dimension of an electrode (m)-   DC Direct current-   E^(→) Electric field vector-   E^(ED) Electric field induced by an electrodeposition between a    source of a countercharge and a first electrode (V/m)-   EMIC 1-Ethyl-3-methylimidazolium chloride-   EMR Electromagnetic radiation-   E_(r) Electric field radial to a point charge-   E_(TC) Electric field induced by second current (V/m)-   E_(θ) Electric field perpendicular to E_(r)-   ε_(o) Permittivity of free space (8.85×10⁻¹² C²/Nm²)-   f Frequency-   F_(DP) Dielectrophoretic force-   F_(EP) Electrophoretic force-   H^(→) Magnetic field vector-   H_(sine) Amplitude of a sinusoidal profile use to approximate    surface roughness-   I Current (amperes)-   i(x) Current at point x on the electrode surface-   i_(ave) Average current density along a rough surface-   i_(H) Current density at the highest features of roughness-   i_(L) Current density at the lowest features of roughness-   I_(peak) Peak current-   I_(peak) Peak to peak current of a waveform-   I_(RMS) RMS Current-   k Dielectric constant of a material-   k 2π/λ-   MCU Main Control Unit-   n Volumetric charge carrier density (e−/m³)-   OCP Open circuit potential-   PCU Power Control Unit-   P_(D) Power at a depth, D, from the electrode surface-   Pe− Radiative power of a non-relativistic, accelerating electron-   P_(ohm) Power dissipated by ohmic losses-   P_(rad) Radiated power-   P_(TC) Applied power of second current-   Q Charge of an electron (1.6 10⁻¹⁹ C/e−)-   R_(CT) Charge transfer resistance of an electrochemical reaction-   RE Reference Electrode-   R_(NF) Distance of the reactive near field from an electrode surface-   R_(peak) Peak resistance-   R_(RMS) RMS roughness of an electrode surface-   R_(S) Solution (electrolyte) resistance-   RTIL Room Temperature ionic liquid-   S_(D) Skin depth-   SHE Standard Hydrogen Electrode-   TC Second current-   v Velocity of charged particle-   V Voltage-   v_(D) Drift velocity of a charged particle-   v_(P) Velocity of propagation-   V_(peak) Maximum voltage of a waveform-   Vpp Peak to peak voltage of a waveform-   V_(RMS) RMS Voltage-   V_(TC) Voltage of second current-   Y Material attenuation constant of second current-   Y_(RMS) Attenuation constant of second current due to surface    roughness-   α Charge acceleration-   γLiénard electric field contraction constant-   λ Wavelength-   λ_(TC) Wavelength of second current-   μ Permeability of electrode-   μ_(o) Permeability of free space (4π×10⁻⁷ N/A²)

Example 1—Smoothness and Uniformity Through Controlled ChargeDistribution

This example demonstrates how charge density increases at surfacecurvature or irregularity. To measure this effect, matching substrateswere processed using conventional electrodeposition or under thedisclosed method. The substrates were then compared to each other.

Referring first to FIGS. 14A & 14B, two 15 mm×18 mm copper electrodeswere machined from an FR1 circuit board (a thin layer of copper over anon-conductive phenolic resin) with two lead attachments 1410, 1420, adeposition area 1420, and five 0.8-mm wide slots 1450. Lead attachment1410 was on a first side 1422 of the slots 1450. A second leadattachment 1415 was on a second side 1421 of the slots 1450 Slots 1450functioned as voids in the workpiece, so that current flow was blockedwith a potential drop on either side of the slot 1450.

FIG. 14A shows the results of electrodeposition of copper at 30 mA/cm²without a second current; that is, under conventional electrodeposition.Darker areas 1425 developed toward the top of the deposition area 1420where charge built up. These darker areas are due to a rougher depositof copper and an increase in copper oxide.

FIG. 14B shows another workpiece resulting from the electrodeposition ofcopper at 30 mA/cm² with a second current of 5 MHz at 10 Voltspeak-to-peak (Vpp) applied between a lead attachments 1410, 1415. Thesame electrodeposition conditions were used in FIG. 14B as in FIG. 14A,but this time with the second current applied across the workpiece, withthe attributes of the current as introduced immediately above.

A comparison at the microscopic level of copper growth with and withoutsecond current is shown in FIGS. 15A and 15B. FIG. 15A depicts anelectron micrograph of a deposit formed from a 1.25 M CuSO₄(aq) usingconventional deposition. This electron micrograph showed rough growth atthe surface, in which scattered the electron beam from the microscope.Porous edges grew outward, while voids were simultaneously filled in.The growth seen in FIG. 15A resulted from kinetic roughening andoccurred when the nucleation rate was high relative to the actual growthrate. At longer deposition periods, these edges propagated faster thanthe voids were filled, leading to more dendritic morphology.

FIG. 15B depicts an electron micrograph of a deposit formed when asecond current of −27 dbm at 1 MHz was applied to the workpiece underthe same conditions as FIG. 15A. For ease of comparison, FIGS. 15A and15B were set with the same size scale. All measurable porositydisappeared on the surface and the growth proceeded with limitednucleation (non-dendritic growth) followed by two-dimensional surfacecompletion. When the parameters were slightly different, the oppositeeffect was observed. Also in FIG. 15B, the current efficiency ofdeposition remained unaltered by the second current. The second currentlowered the nucleation rate while the overall rate of growth remainedconsistent as two-dimensional expansion. The electric field of secondcurrent increased the surface diffusion rate of adsorbed metal insteadof immediate nucleation with complete charge transfer. Therefore, theentropy of the surface was lower than normal. The degree ofcrystallinity can be controlled by modulating the second current toachieve the desired deposit properties.

Conventionally, irregularities are managed with slower depositioncurrent densities, chemical additives (levelers/brighteners), largeelectroplating baths, or anodes on all sides. Applying a second currentinstead provided a simple means to reduce reliance on or avoid theseconventional practices. The uniform distribution of charge afforded bysecond current reduced the disproportionate growth normally observed atedges and points. Consequently, the uniformity of growth became lessdependent upon the relative position of an anode.

By inducing high frequency movement of the electrons on the surface ofthe first electrode under the methods used in FIGS. 14B and 15B, thecharge was more evenly distributed across the surface than usingconventional electrodeposition in FIGS. 14A and 15A, resulting inuniform deposit across the entire surface of the workpiece. Thesurface-distributed charge arose from multiple mechanisms operatingtogether. On average, the electrode was uniformly polarized, which ledto a uniform concentration distribution of reactant species near thesurface.

Adhesion of electrodeposited metal was challenging because native oxidelayers form on metal surfaces in the presence of oxygen or moisture.These layers are conventionally removed using strong acids to etch themetal surface before new metal is deposited without allowing significantoxygen to enter the system at any point. Mechanically strong bondformation is a higher energy process. This is part of the reasondeposited layers can grow on a substrate only to be easily peeled offlater, and why the edges of two first electrodes may grow together withdeposition but fall apart upon later handling.

By using electrolyte chemistry that supported reversible orsemi-reversible corrosion, treatment with strong acids was avoided byfirst corroding the surface oxide layer into solution to expose baremetal at the surface of the first electrode. Corrosion-based surfaceexposure may be performed with the first current between the firstelectrode and a source for a countercharge, or independently of a sourcefor a countercharge with just the second current running through thefirst electrode.

Superior adhesion of a metal onto a substrate was also obtained withoutconventional surface pre-treatments using DC or alternating AC/pulsecorrosion first currents, shown in FIG. 16. During Period A, the pulsesalternated between neutral and corrosion-inducing potentials. Corrosionat ≥100 mA/cm² encouraged the release of bulk pieces of the substratevia corrosion along grain boundaries. The pulses had a defined pulselength of uniform or non-uniform duty cycle and a DC offset indicated bythe dashed line. Once the surface was roughened during Period A, the DCoffset was transitioned to more a reducing potential over Period B, sothe ratio of reducing to oxidizing current slowly increased. DuringPeriod C, the pulses were entirely neutral or reducing. The finalmagnitude of the reducing pulse equaled that at which deposition currentwas maintained thereafter.

The duration of Period C may be prolonged if significant rougheningoccurred during Period A. The frequency of pulses was usually betweenabout 1 Hz and about 1 kHz (and lower for surfaces with significantpolarization resistance). Faster frequencies become ineffective due tocomparatively slow mass transport rates. DC current may instead be usedfor Periods A and C, only. Examples of systems suitable for DC currentincluded the most non-reactive metals in aqueous solutions, or reactivemetals in ionic liquids, in which the most highly oxidized metal speciesremains reducible to a metallic state.

Period B was effective at reducing thick passivation layers on the firstelectrode. Conventional pulse deposition or reverse-pulse depositionmethods are not sufficient to remove the passivation layers on morereaction metals like Fe, Al and Ti. For example, on a passivated nickelsurface, the passivation layer comprised a mixture of nickel oxide andnickel hydroxide atop the outer metallic boundary. Charges musttransverse this layer through each oxidation state before reducingcompletely. In contrast, deposition onto non-passivating surfaces suchas Au went by comparatively simple adsorption and charge transfer steps.

Example 2—Surface Repair

This example demonstrates the effectiveness of the second current inrejoining the surface of a first electrode. FIGS. 17A-L shows aprogression of surface smoothing on a copper electrode 1700 of 1 cm².FIG. 17A is the first image in the series, which was cut down the middle1710 with shears before the rejoining process began. Several horizontalimprints 1720 are labeled in FIG. 17A (the same imprints are alsoevident in the other views through FIG. 17J) are apparent from pliersused to straighten the workpiece after shearing The first electrode, inthis case the sheared copper sample, is viewed from the perspective ofthe source for a countercharge through the electrolyte (one-halfsaturation CuSO₄(aq) at ambient temperature).

At the start of the process, the Cu surface received no chemicalpre-treatment (FIG. 17A). To roughen the surface for demonstration ofcrack filling, the copper workpiece (first electrode) was exposed to a100 mA first current for several minutes (FIG. 17B). At this highcurrent density, the metal from the first electrode primarily corrodedin small chunks, starting at the outer edges of the first electrode.After several minutes, the surface of the first electrode wassubstantially rough (FIG. 17C). This roughening was much more thanneeded to remove surface oxides and promote adhesion of deposited metal,but the extreme roughness provided a useful visual of the effects of thesecond current.

The first current was applied at 15 mA (−0.5 V) from the source of acountercharge through the electrolyte, while two second currents wereapplied across the copper workpiece (second electrode) (FIG. 17D). Thefirst transverse current (TC₁) was sinusoidal at 1 MHz 3 Vpp (50 ohm)between leads positioned on the workpiece equidistant from the shear.The second transverse current (TC₂) had the same attributes as the firstbut phase offset by 90°. Two-dimensional growth dominated despite aperpendicular positioning of the source of a countercharge to thesurface of the workpiece as shown in the sequence of images from FIG.17D to 17I. Normal charge density at edges of roughness was avoided.Instead, the horizontal imprints 1520 were filled in, which is alsoshown in the sequence until they disappear after having been filled asshown in FIGS. 17K and 17L. As processing progressed, the originalsmooth surface was restored resulting a relatively smooth workpiece withthe shear filled as well as the imprints (FIGS. 17J-17 L). As most ofthe surface of the first electrode 1700 was restored, remaining valleyshad a planar bottom and growth proceeded vertically until the valley wasfilled in with new metal-metal bonds formed between metal from theelectrolyte and the metal of the walls of the valleys.

An appropriate waveform and parameters should be selected to induce thefilling effect. This example was performed with simple sinusoidal wavesat a fixed voltage, frequency, and phase offset. Had parameter settingsbeen dynamic and able to adapt to the changing surface over time, aswith sensory feedback, the surface features of the first electrode maybe filled and smoothened simultaneously. Other factors that may effectthe deposition and bonding are the position of the leads inducing thecurrent across the workpiece, as well as the position of the source ofcountercharge relative to the workpiece, among other factors.

With no second current, the sample would have only demonstrated theoutcome of conventional electrodeposition. For example, from FIG. 17Conward, deposition would have propagated roughness instead of smoothingand filling.

Example 3—Second Current Controlled Adhesion

This example illustrates that the second (transvers) current can be usedalone without absent deposition or corrosion under the first current.The second current alone was used at high potentials and modestfrequencies to effect a high enough slew rate. FIGS. 18A and 18B areelectron micrographs of a workpiece showing corrosion-based surfaceroughening caused by the transverse current. In particular, a relativelyhigh voltage of 7 kV at 34 kHz, limited to 30 mA, induced significantsurface roughening in less than 5 seconds. The surface had thepassivation layer removed along with some metal from the workpiece. Theprocess may be influenced toward finer removal of material, or theprocess may increase corrosion using a first current between theworkpiece and a source for a countercharge, or by modulating the secondcurrent to higher frequencies or higher powers. Conventional surfacepretreatments were unnecessary when applying the second current,particularly when the most highly oxidized metal species remainedreducible in the electrolyte.

The transverse current reduced the level of porosity that wouldotherwise appear during electrodeposition. This effect also made newmaterial adhere better by improving the deposit quality at the substrateinterface. Epitaxial growth caused the new layer of deposited metal toadopt the crystal orientation of the workpiece. Controlling thismechanism promoted good adhesion, and was useful when the layer andsubstrate were the same material, or were two materials with similarlattice spacing. With two crystallographically dissimilar materials,forced epitaxial growth can cause significant strain stored at theinterface that will be prone to cracking. Here, the transverse currentwas modulated to roughen the surface or reduce porosity while allowingthe relief of strain during deposition.

Example 4—Pressed Powder Corroding Electrode

Pressed power corroding electrodes were also investigated. FIG. 19A isphotograph of a corroding electrode formed from pressed powder. Thecorroding electrode may be a source of countercharge, comprising mixedparticles of various size, geometry, composition, and conductive ordielectric. The corroding electrodes included CuSO₄ with the metalparticles, which were pressed together to replenishing the electrolyteas the electrode dissolved during operation. FIG. 19B is an electronmicrograph of a deposit made using the corroding electrode of FIG. 19A.

Example 5—Bonding Using Computerized System

To illustrate bonding using a computerized system described herein,reference is made to the device 2000 at FIG. 20. The electrolytecontaining AlCl₃-EMIC is loaded into a reservoir of the main controlunit (MCU) 2010 or the applicator 1100. The MCU 2010 is programmed toapply first current and second current power schemes selected for theAl—Fe electrolyte/corroding electrode combination. The device 2000 ispowered from an external source such as a wall plug 2015.

Still referring to FIG. 20, The operator may attach two leads 2030, 2035of the current collector cable 2040 to both portions 113, 114 of thefirst electrode 110 to polarize the first electrode 110 for the firstcircuit, and also to apply second current between the two leads 2030,2035 through a surface of the first electrode 110. The portions 113, 114are positioned relative to one another or in direct contact with oneanother to ensure a more even charge distribution across the firstelectrode 110. The user 2050 may forgo the leads 2030, 2035 for thesources of a countercharge built into the tip 1170, 1175 of theapplicator 1100, as shown in FIG. 11. Alternatively, the user 2050 mayuse both, with the leads 2030, 2035 proving broad second current whilethe counterelectrodes of the applicator 1100 localize the second currentacross the area of the tip.

The electrolyte comprises polydisperse Fe particles having an averagediameter between about 0.5 μm and about 1 μm, covered in 2 or 3 atomiclayers of aluminum. The electrolyte also contains dissolved AlCl₃ at amolar ratio of about 1:1 with EMIC. See Example 12 for more details ondeposition chemistry.

Within the applicator is a corroding electrode as a source of acountercharge comprising the same Al/Fe particles pressed into a 1-cmwide, 1-cm high pellet. As this electrode corrodes, the Al/Fe particleconcentration of the electrolyte is replenished. The Al coating aroundeach particle allows them to dissolve with an electroactive, reduciblesurface otherwise impossible for Fe in EMIC.

The material dimensions and composition are stable at temperatures below80° C. Therefore, the operator may set the interior temperature of theapplicator to 60° C. to promote deposition. The MCU's 2010 software mayaccount for temperature and may modulate the applied powerautomatically.

The operator 2050 may manipulate the applicator 1100 to directly contactthe junction 500 of the portions 113, 114 of the first electrode 110with electrolyte from the tip. By manipulating the applicator 1100, theoperator 2050 may activate one or more controls 1180 on the applicator1100. These controls may execute the power sequences specified in thesoftware controlling the MCU 2010. The sequence may include current topositively polarize the first electrode, removing the passivation layeron the surface. This step may be followed by a negative DC polarizationof the first electrode with square wave second current at 1 kHz and 10dbm and DC offset of 5 V. This waveform for the transverse current toimparts smoothness during deposition of the dissolved Al and Al—Feparticles. The transverse current also activates the gap defined by thetwo portions 113, 114 of the first electrode 110 for deposition.

Capacitance- and impedance-based feedback measurements may inform theMCU of changes in the deposition environment. The feedback can detectsolids suspended or dissolved in electric field between the workpieceand the source of a countercharge. The feedback can detect thedecreasing surface area on the workpiece, which indicates that thesurface has been smoothened. The feedback can also detect that ajunction has been closed with newly deposited material. The feedback mayallow the MCU to automatically modulate the applied potentials andcurrent density.

Once the gap is filled, the DC offset is decreased to 0 V while thesecond current switched to 1 MHz and −60 dbm to continue impartingsmoothness to later layers over the junction. The operator 2050 maystart, stop or regulate the flow of electrolyte and power through allcircuits in this way. The junction 500 is replaced by deposited materialwith chemical and physical properties similar to or the same as the twooriginal portions 113,114 of the workpiece 110.

Example 6—Repairing Chemical Tank

Methods of the present disclosure may be used to repair a crack in theexterior of a tank storing several tons of chemicals. The disclosedmethod avoids the dangers of hot work (welding, brazing, cutting)normally used for these repairs, which could ignite or react thechemicals in the tank. Also, the tank need not be removed from servicefor repair, avoiding the loss of productive time and minimizingenvironmental exposure.

To perform the method, the surface of the crack is cleaned to removepaint, grease and dirt. With the surface clean, the worker applies anapplicator patch over the crack. The patch contains a viscous Feelectrolyte containing Fe particles having a diameter between about 100nm and about 300 nm, and a Fe corroding electrode as the source of acountercharge and additional Fe particles. Other metal species may beincluded in the electrolyte to match the alloy of the tank. Two contactson the pad are oriented on either side of the crack so the secondcurrent propagates transverse to the crack's length. The patch, andseveral others like it, may cover other cracks on the tank. All patchesare connected to a remotely controllable MCU.

The worker leaves the vicinity of the tank and safely controls the MCUremotely. The MCU is programmed to first apply a corrosion-rougheningstep through the electrochemical circuit. The roughened surface isprimed for new metal deposition. Next, the MCU proceeds with slowdeposition with second current of 10 dbm at 4 GHz and DC offset of 0.5V. The second current frequency is chosen because it is sufficientlyfast while not stimulating dangerous chemicals stored in the tank. Poweris lost from dissipation across the crack. Power is set to 10 dbmcompensate for this dissipation.

Moreover, Fe particles in the electrolyte are sufficiently small to fillthe width of the crack. The Fe particles are directed by the transversecurrent, the potential that it induces, the electrophoretic force of the0.5-V DC offset in the waveform. In some instances, particularly at highfrequencies that exceed the mobility of the charged species such as 4GHz, the Fe particle may be too large to oscillate much at the highfrequency. However, the transverse current can still induce aneutralizing effect (V_(AVE) ca. 0) at sharp edges of the particles aswell as the substrate. As a result, charged species are directed todeposit more uniformly regardless of surface features.

The repair can be made with applying only the needed energy to the tank.When the repairs are complete, the worker removes the patches from thetank. Repairs can be made more frequently because the disclosed methodsare ease and safe compared to conventional dangerous hot work. Theworker or his peers can assess the quality of the repair and maintainstandards and process control following data review. And the quality andproperties of the deposited metal are much higher than conventionalwelds, are better matched to the tank base material by selection of themetal species for deposit, and are more uniform than would otherwise bepossible with conventional hot work repairs.

Example 7—Anti-Corrosion Method

This example describes a corrosion suppression system (CSS), whichgreatly extends the life of heat exchangers. A 12″ length of copperalloy tubing (½″ outer diameter) transports effluent at 80° C. from awater purification system to a heat exchanger. The effluent is highlysaline water (120 g/kg) with dissolved ammonia and metal ions from apotable water stream of a reverse osmosis system. The inner surface ofthe tubing is thinly lined with a self-healing polymer coating, whichprotects the copper alloy from corrosion. The lining minimally affectsthe heat transfer of the effluent to the copper alloy. Without thelining, salt and ammonia would oxidize and corrode the copper alloy.Once pitting occurs from corrosion, the tubing would be much moresusceptible to failure.

As effluent flows through the tubing, the CSS monitors and passestransverse current along the length of the tubing. For this monitoringmode, the transverse current is applied as sinusoidal waveform at 0 dbm,50 kHz, and pulsed for 100 periods each 5 min, followed by a restingphase. The self-healing polymer evenly distributes the transverse fieldstrength across the tubing. An electric field results from the passageof transverse current. The conductivity of the effluent attenuates thiselectric field. The exterior of the tubing is open to air with adielectric constant of 1, while the polymer exhibits a value of 2.2.These parameters define the baseline for the impedance measurement.Changes in integrity of the lining, the temperature, the fluidcomposition, and the flow rate of effluent are detected from deviationsin the baseline impedance measured on the transverse current.

After several days of continuous operation near the temperature andpressure limitations of the self-healing polymer, a defect develops inthe lining that allows the effluent to directly contact the copperalloy. Normally, the copper alloy underneath the polymer would corrodeand pit at the defect, compromising the mechanical integrity of thesystem. The CSS, however, detects the defect from a change in thebaseline impedance caused by a sudden increase in the impedance signalwhen the effluent directly contacts the copper alloy. In response, theCSS switches from the monitoring mode using the periodic transversecurrent to a repair mode using a continuous transverse current at 0.2dbm and 30 MHz. The higher power of the repair mode compensates for thesignal attenuation. The higher frequency of the continuous transversecurrent outpaces the rate of the corrosion reaction, so that theprogression of corrosion is halted and the defect is repaired. Thewavelength of the transverse current is selected to be less than thelength of the tubing. The polar symmetry of the sinusoidal waveformdisrupts the flow of electrons and ions near the defect, which wouldnormally facilitate corrosion. A net change is not induced in transversecurrent, because the mean potential at the defect remains at zero.

With the corrosion stabilized, the surrounding polymer is not furthercompromised. The self-healing polymer at the defect can recover, forexample via internal hydrogen bonding catalyzed by solutes in theeffluent. Once recovered, the self-healing polymer again isolates thecopper alloy from the effluent. The impedance signal returns to isbaseline. The CSS switches from the repair mode back to the monitoringmode using a pulsed transverse current.

Example 8—Two-Dimensional Computer Simulation of the Bonding Method

A two-dimensional computer simulation explored the charge distributioninduced by transverse currents no offset and at a 180° offset. Thesimulation revealed that transverse currents induced non-uniformities inthe electric field, similar to roughness in the physical topography of aworkpiece. These non-uniformities would be counterproductive to uniformdeposition. Modulating the electrodeposition and the transverse currentstogether overcame this simulated effect without dramatically increasingthe total electric field.

Referring to FIG. 21, a simulated device 2100 comprised two anodes2120A, 2120B and a cathodic workpiece in two segments (2110A, 2110B)having a gap 2150 between the segments 2110A, 2110B. The workpiece2110A, 2110B was in electrical communication with the anodes 2110A,2110B through an electrolyte 2140. In the simulation, the electrolyte2140 was saltwater, the “conductivity(2)” parameter was 5, the time was9.75 μs, the slice was the electric field norm (V/m), and the relativeangle between the electrodeposition and transverse current (phi) was 0°.The arrows 2133 are the electric field lines.

This simulation of FIG. 21 resembles conventional pulse plating whereboth the left 2110A and right 2110B regions of the workpiece were pulsedevenly. Here, the transverse current pulsed the workpiece 2110A, 2110Bwithout pulsing the anodes 2120A, 2120B. The magnitude of the electricfield lines 2133 is illustrated by the length of the arrows. Theelectric field across the surface was uniform, particularly along thez-axis.

Low charge density is shown in blue and strong charge density showing inred. The charge density 2122, 2125 is greatest between the anodes 2120A,2120B and the workpiece 2110A, 2110B, especially at the corners 2121,2123 of anode 2120A and the corners 2124, 2126 of anode 2120B. Littlecharge density was seen in the gap 2150. The electric field lines 2133were perpendicular to the workpiece 2110A, 2110B. Referring to FIG. 23,the oscillation minima and maxima were between about 450 V/m and about1050 V/m.

Referring now to FIG. 22, a simulated device 2200 comprised two anodes2220A, 2220B and a cathodic workpiece in two segments 2210A, 2210Bhaving a gap 2250 between the segments 2210A, 2210B. The workpiece2210A, 2210B was in electrical communication with the anodes 2210A,2210B through an electrolyte 2240. As with the simulation from FIG. 21,the electrolyte 2240 was saltwater, the “conductivity(2)” parameter was5, the time was 9.75 μs, and the slice was the electric field norm(V/m). In the simulation of FIG. 22 the relative angle between theelectrodeposition and transverse current (phi) was 180°, where the left2210A and right 2210B regions of the workpiece were pulsed so that thevoltage on the left had the same magnitude but opposition polarity asthe voltage on the right. The arrows are the electric field lines above2233A the workpiece and on the backside of the workpiece 2233B.

The electric field 2233A was very strong along the y-axis. As thetransverse current cycled through a full period, the magnitude of theelectrodeposition field arrows 2233A above the workpiece 2210A, 2210Bbecame uneven, particularly along the z-axis. This behavior workedagainst a uniform deposit, even as the field strength along the y-axisaided uniform deposition. An electric field 2233B was also induced onthe backside of the workpiece 2210A, 2210B near the gap 2250. The chargedensity 2222, 2225 was greatest between the anodes 2220A, 2220B and theworkpiece 2210A, 2210B, especially at the corners 2221, 2223 of anode2220A and the corners 2224, 2226 of anode 2220B. Charge density was alsoseen in the gap 2250, where the electric field lines 2233A bent towardto the workpiece 2210A, 2210B near the gap 2250.

Referring to FIG. 24, the maxima increased to over 6000 V/m. Such highfield strength along the z-axis may cause roughness on the workpiece andburnout via oxidation and oxygen adsorption. However, by inverselymodulating the electrodeposition against the transverse current, theelectric field strength perpendicular to the workpiece can be stabilizedeven when the transverse current increases. This modulation leads tosmoother deposits without decreasing the average rate of deposition.

Example 9—Bonding Method Using Copper Metal Bonding Method

This example showed copper joining workpieces of copper and steel andanalyzes how the electrodeposition and transverse currents combine inthe signal generator. In one experiment, two 5″×1″ pieces of 0.08″ thickcopper sheet were joined along their longest dimensions. In a relatedexperiment, two pieces of steel were joined using an electrodepositioncurrent of −300 mA. Samples prepared using conventionalelectrodeposition methods and the bonding method disclosed herein werecompared to each other.

A high-density polyethylene (HDPE) applicator with a dielectric constantof about 2 was used. The electrolyte was aqueous saturated CuSO₄ with noadditives. Two copper anodes (5″×0.54″×0.125″) were used withoutisolating bags. Electrodeposition proceeded with and without AC waveformmodulation of the electrodeposition current relative to the transversecurrent. When present, the transverse current was applied with asinusoidal waveform having an amplitude of 120 mA to balance theelectric field parallel to the surface. The equivalent impedance of thetransverse current and electrodeposition at the cathodes was 2.4 ohmwhen combined.

Referring to FIG. 25, the right transverse current was applied via anelectrical contact, Channel A (ChA), to the right workpiece. The lefttransverse current was applied to the left workpiece via Channel B(ChB). ChA and ChB included two equal transverse currents at a 180°phase offset at 100 kHz. As the strength of the ChA-ChB signalincreased, the electrodeposition current decreased, so that the totalcurrent perpendicular to the surface remained within acceptabletolerances and did produce rough deposits.

A composite waveform resulted when the electrodeposition current wascombined with the transverse current in the left and right channels.FIG. 26 compared the original transverse current to the new compositewaveform. The difference between ChA and ChB were the same between bothwaveforms. The vector of the field changed at 0-π compared to π-2π. Thischange distinguished the signals of the disclosed methods from thoseused in conventional pulse plating, which does not have the describedfield changes. Here, the net current remained negative, facilitatingcontinuous electrodeposition.

Referring to FIG. 27, the signal could be mistaken for conventionalpulse plating in a scalar interpretation. However, this interpretationdoes not consider the vector of the signals constituents resulting fromthe electrodeposition and transverse currents. In conventional pulseplating, the anode experiences the same but opposite polarity pulsing asthe cathode. In contrast, in the disclosed bonding method the anodeexperienced only some pulsing in FIG. 27. Specifically, the anodeexperienced only the pulsing of the uncombined electrodepositioncurrent.

Referring to FIG. 28, the parallel current imparted inside the junctionbetween the two workpieces was the same compared to the original rightand left transverse currents and to the combinedtransverse-electrodeposition signals. Modifying waveforms of theelectrodeposition and the transverse currents may alter the duty cyclein the junction. For example, a duty cycle of 80% positive current and20% negative current promotes the deposition of material inside thejunction from one side of the junction to the other side of thejunction. This duty cycle may be changed gradually during the process,so that the balance of positive and negative current promotes moregrowth from the other side of the junction.

Referring to FIG. 29, an equivalent impedance Z₁ was assumed for thetransverse current Z₂ and the electrodeposition current Z₃ applied inparallel. The transverse current operated with an impedance of 6 ohms,due to the impedance of the AC signal generator, the cables, and mostlythe low impedance of the electrodes. The electrodeposition currentoperated with an impedance of 4 ohms, due to the resistance of theelectrolyte, the impedance of the bias-tee that combined the transversecurrent and the electrodeposition signals, and the polarizationresistance at all electrodes. At FIG. 30, the calculated potentials forChA and ChB used the equivalent impedance. The exact potential variedwith hardware, temperature, concentration, and pH of the electrolyte.

The original 5″ long sample of joined copper workpieces was cut in halfto access adhesive strength of deposited metal. FIGS. 31 and 32 show SEMimages of the bottom of a copper sample treated conventionally, whichaccelerated growth of metal at the edges facing the anode. The gapbetween the two workpieces filled poorly and the joint was weak. FIGS.33 and 34 show SEM images of the bottom of a copper sample treated withthe bonding method disclosed herein. The strong electric field withinthe gap caused metal fill the gap flat and uniform. This flat geometrywas much stronger than the convex geometry conventionally achieved.Elongated metal grains in the deposited metal aligned with the electricfield from the transverse current. Modulating the electrodepositioncurrent relative to the transverse current controlled of the fieldstrength perpendicular to the surface, while allowing the field strengthparallel to the surface to fluctuate. Further, the transverse currentsuppressed the accelerated deposition of metal that would normally occurat the anode-facing edges of the workpiece. This suppression preventedthe gap from being pinched shut at the top before filling with metal,resulting in joint strength far superior to conventional and previouslyknown methods.

Example 10—Incident-Reflection Method

This example demonstrated reflection of an incident transverse current(iTC) on a surface of a workpiece to generate a reflected transversecurrent (rTC). The iTC and rTC signals interacted to affect thedeposition using the disclosed bonding method.

A sample was prepared from a FR1 circuit board coated with copper foilon both sides. Electrodeposition occurred at −1 V, using two copperanodes on either side of the circuit board. The transverse current wasapplied through two channels via an electrical contact on each side ofthe circuit board. Both channels applied a transverse current at 100 kHzand 1.5 Vpp with a 180° phase offset. The two sides of the circuit boardhad no direct electrical contact.

The incident transverse current (iTC) originated from the left side ofthe circuit board. The iTC signal changed as it travelled across thesurface of the circuit board, because the electrodeposition and theelectrolyte absorbed energy from the iTC. The remaining, unabsorbedenergy in the iTC continued to travel across the surface until itencountered the right side of the circuit board. The iTC reflected back,generating the reflected transverse current (rTC). When iTC encounteredrTC, their energies superimposed, like ripples in a pond. When thesuperimposition provided more energy at a point, the electrodepositionincreased at the point as a function of the rate of the electrochemicalreaction. The frequency and power of the iTC could be swept nonlinearlyto promote a uniform electric field across the surface of the workpiece.Alternatively, the frequency and power of the iTC can target particularfeatures or topographies on the surface of the workpiece.

Referring to FIGS. 35 and 36, the deposited copper had a differentfinish, texture and morphology than the copper of the circuit board.FIG. 35 was generated from a secondary electron detector (SED), showingcontrast between surface textures. FIG. 36 was generated from abackscattered electron detector (BSD), showing contrast between therelative differences in atomic weight of different elements. The SEDshowed the two regions differed in fine textures, though broadermorphology was similar between regions. The BSD showed the regionsdiffered in average elemental composition.

FIGS. 37A-C the purity of the copper was uniform, although morphologyand nucleation differed between areas just a few microns apart.Elemental mapping in FIG. 37A showed uniform copper distribution acrossthe two regions. Overall, oxygen concentration was low (FIGS. 37C andD), but the oxygen levels were slightly greater on the bottom region(FIG. 37B). This concentration difference is not because the lower areadeposited more oxygen into the bulk, but instead because the surfacearea was greater due to increased roughness. Therefore, more surfacearea and more oxygen were exposed to the detector at the bottom region.

Example 11—Al—Fe Deposit

This example demonstrated successful deposition of a difficult alloyfrom an ionic liquid via co-deposition of particles. Particlesoriginated from solution or from a corroding anode. The corroding anodewas the preferred source because a greater number of particles wereoccluded during deposition.

The ionic liquid was a 1:20 molar ratio of trimethylamine hydrochloride(TMA-HCl) and urea. The anode was an Al—Fe composite having Al particleswith an average diameter between about 0.5 μm and about 2 μm, and Feparticles with an average diameter between about 10 μm and about 1 mm.In some samples, an Fe sheet anode was also used with the Al particlesmixed into the electrolyte. The cathode substrate was a steel coupon(¾″×¾″). The solution temperature was between about 100° C. and about150° C. An electrodeposition current of −1.4 V was used.

FIG. 38A is the elemental analysis of a vertical cross-section of thedeposit showing iron, aluminum, and carbon. FIG. 38B was a scanningelectron micrograph composite of the iron, aluminum, and carbon signals,showing the codeposition of aluminum (orange) and iron (yellow) at thesurface of the steel substrate (yellow and blue). FIGS. 38C-E are thetwo-dimensional elemental maps for each iron (FIG. 38C), aluminum (FIG.38D), and carbon (FIG. 38E).

Example 12—Deposition from an Aluminum Corroding Anode

This example demonstrated another deposition of the Fe—Al alloy, hereusing a corroding anode as the metal source. In this example, theelectrolyte was an ionic liquid containing an about 1:1 molar ratio ofethylmethylimidazolium (EMIC) and AlCb. The active species in thiselectrolyte was Al₂Cl₇. The Al was dissolved in solution, and the ironoriginated from a corroding particle anode or a plate anode (See Example11 above). The workpiece was copper (½″×¾″). The solution temperaturewas 30° C. The electrodeposition current was −1.6 V±0.2 V.

FIG. 39A is a scanning electron micrograph of the deposition. FIGS. 39Band 39C are the two-dimensional elemental maps for aluminum and iron inthe sample, respectively, showing an approximately 1:1 aluminum-ironalloy deposited from the ionic liquid onto the copper workpiece. FIG.39D is an elemental analysis confirming that the sample contained iron,aluminum, copper, carbon, oxygen, and chlorine.

Example 13—Fe—Zn Alloy Deposit

This example demonstrated Zn—Fe alloy deposition from an ionic liquidusing a pressed powder electrode. An ionic liquid was prepared from a1:2 molar ratio of choline chloride and urea. The zinc and iron sourcesfor the deposit came from the anode and dissolved salts. The anodestested were an iron anode, a zinc anode, or a Zn—Fe anode made ofpressed powder or other preparation. A solution of 0.2 M ZnCl₂ preparedin the ionic liquid. Up to 0.3 M FeCl₃ was also added to the solution.The workpiece was mild steel (¾″×¾″). The solution temperature was 85°C. The electrodeposition current was −1.8 V.

FIGS. 40A-H show a 5:4 (mol/mol) iron-zinc alloy was deposited fromionic liquid. FIG. 40H shows an electron micrograph composite of theelectron micrograph (FIG. 40A), and the two-dimensional elementalcontents for iron (FIG. 40B, yellow), zinc (FIG. 40C, light blue),carbon (FIG. 40D, cyan), chlorine (FIG. 40E, green), and oxygen (FIG.40F, dark blue), showing the codeposition of zinc and iron to form thealloy. FIG. 40G shows the elemental distribution in the sample, showingthat the sample contained iron, zinc, carbon, oxygen, and chlorine

Example 14—Plating Copper onto a Woven Workpiece

This example compared copper bonding to carbon cloth via conventionalelectrodeposition at (FIG. 41A) and the disclosed bonding methods usingtransverse current (FIG. 41B). For each sample, copper (3″×1″×0.032″)with a <110> crystal face was joined to 3 k woven carbon fiber cloth(3″×1″). The electrolyte was saturated CuSO₄(aq). The anodes were alsoCu <110>. The bonding current density was 0.6+/−0.02 mA/mm². Whenpresent, the transverse current was applied through two channels, usinga 180° phase offset, 5 Vpp, 100 kHz with a saw waveform. One channel wasconfigured for the copper workpiece and the one channel was configuredfor the carbon cloth.

Referring to FIG. 41A, the junction 4150 between the carbon cloth 4115and the copper workpiece 4110 did not receive as much new copper as theareas 4151, 4152 farther away. The junction 4150 had gaps where theweave of the underlying carbon cloth 4115 is still visible. As such, thejoint between the two workpieces 4110, 4115 was very weak. Depositionnear the junction 4151, 4152 was rough. Deposition on the copperworkpiece 4110 was smoother and more nearly matched the <110> crystalphase of the copper workpiece 4110.

Referring to FIG. 41B for which a transverse current was applied duringbonding, the junction 4155 between the carbon cloth 4115 and the copperworkpiece 4110 received ample new copper. The junction 4155 had no gaps.The weave of the underlying carbon cloth 4155 was not visible. As such,the joint between the two workpieces 4110, 4115 had a strength similarto that of the original copper workpiece 4110. Moreover, the areas 4156and 4157 adjacent to the junction 4155 also had thick deposits of newcopper. The deposition across both the workpieces 4110, 4115 was smoothand nearly matched the <110> crystal phase of the copper workpiece 4110.

The bonding method of this example can also be applied to anon-conductive woven workpiece, such as a woven para-aramid syntheticfiber (Dupont™ Kevlar®). Because Kevlar® is not conductive like copperor semi-conductive like carbon, the woven workpiece is first impregnatedwith a metal salt, such as NiCl₂(aq), before further processing. Anynon-conductive woven workpiece, such as cotton cloth or polyester cloth,may be pretreated in this way. The treated woven workpiece is processedusing a method described to deposit aluminum, titanium, or another metalor alloy. Kevlar® or other non-conductive workpiece may be shaped intopanels or shaped to a mold before deposition, so that the metallizationlocks the fabric into place.

Example 15—Further Examples of Joining Separate Workpieces A. JoiningCopper to Nickel

A copper <110> workpiece (3″×1″×0.032″) was joined to nickel <200>(about 2.5″×1″×0.062″) using copper. The electrolyte was saturatedCuSO₄(aq). The anodes were also Cu <110>. The electrodeposition currentdensity was 0.6 mA/mm². The transverse current was applied through twochannels, with one channel configured to the copper workpiece and theother channel configured to the nickel workpiece. The transverse currentwas applied with a 180° phase offset at 5 Vpp and 100 kHz in saw toothwaveform. These were the same parameters for the transverse currentconditions as the copper-carbon cloth at Example 14.

Referring to FIG. 42, the junction 4250 between the nickel 4215 and thecopper workpiece 4210 received ample new copper. The junction 4250 hadno gaps. As such, the joint between the two workpieces 4210, 4215 wasmechanically strong. Moreover, the areas 4251 and 4252 adjacent to thejunction 4250 also had thick deposits of new copper. The depositionacross both the workpieces 4210, 4215 was smooth, although the junction4250 received the most new material.

The differences in thickness and the similarity in conductivity betweenthe nickel 4215 and the copper 4211 workpieces probably contributed tothe junction 4250 not being as strong as the junction 4155 betweencopper 4110 and carbon cloth 4115 (FIG. 41B, Example 14). The thicknessof the nickel workpiece 4215 was twice that of the copper workpiece4211, while the conductivity between copper 4211 and nickel 4215 wascloser than the conductivity of copper to carbon fiber. The Vpp could bedecreased to lessen spikes in the electrodeposition field perpendicularto the surface, while maintaining a large potential difference in thejunction. The phase offset of the transverse current to theelectrodeposition current could be reduced to 90°. This reduction wouldalso lessen the size of spikes in current density at the edge of thenickel workpiece. The frequency could be increased into the MHz regionto suppress faster growth at edges, especially at the nickel edge whichis already thicker.

B. Joining Brass to Aluminum

In another experiment, brass (3″×1″×0.032″) was joined with copper toaluminum alloy 7075 T6 (about 2.5″×1″×0.032″). The electrolyte wassaturated CuSO₄ (aq). Because an aqueous electrolyte was used, thealuminum was coated in zinc before the bonding. The anodes were Cu<110>. Electrodes has a 1-mm spacing. The electrodeposition currentdensity was 0.36+/−0.02 mA/mm² for one hour. The transverse current wasapplied via a single channel at 10 Vpp/1 App and 100 Hz.

Referring to the photograph at FIG. 43A, the junction 4350 between thealuminum 4215 and the brass workpiece 4310 received ample new copper.The junction 4350 had no gaps. As such, the joint between the twoworkpieces 4310, 4315 was mechanically strong. Moreover, the areas 4351and 4352 adjacent to the junction 4350 also had thick deposits of newcopper. The deposition across both the workpieces 4310, 4315 was smooth,although the junction 4350 received the most new material. FIG. 43Bmagnifies the junction 4350. The regions 4351, 4352 adjacent to thejuncture 4350 show ripples from convection in the electrolyte duringdeposition.

FIG. 43C shows the junction 4350 between the aluminum 4215 and the brassworkpiece 4310 after an additional hour of electrodeposition at1.21+/−0.02 mA/mm². The transverse current was applied via a singlechannel at 1.5 Vpp/50 mApp and 100 Hz with a forward ramp waveform. Thiswaveform more strongly influenced the diffusion of charged species inelectrolyte than expected. Power shifted to the electrodepositioncircuit with an increase in current density of about 3.3. The transversecurrent dropped to about 18 mWPEAK. This combination ofelectrodeposition and transverse currents increased the roughness of thedeposit at the junction 4350 and in the regions 4351, 4352 near thejunction.

C. Joining Copper Sheets

This example shows copper workpieces joined with copper under differingconditions using the disclosed bonding method. Copper sheets (5″×2″)were cut in half, deposited with material, and then bent along theirjunction to test mechanical strength. Perpendicular shearing & Bendingalong both axis of the junction.

FIGS. 44A & 44B show copper sheets joined with the transverse currentperpendicular to the junction. The samples were prepared with anodes onboth sides of the workpieces. The bonding currents were 0.60+/−0.02mA/mm² and 0.15+/−0.02 mA/mm². The transverse current applied through asingle channel configured at the middle of the workpieces about 0.75inches from the junction. The transverse current had a sine waveform at20 Vpp/800 milliamperes peak-to-peak (mApp) and 100 Hz. The process ranfor 15 hours. These samples were mechanically strong and had a slightlydull finish.

FIGS. 44C & 44D show copper sheets joined under conditions whichproduced a shiny finish, but displayed greater bending fatigue. Anodeswere placed on both sides of the workpieces. The bonding current was0.60+/−0.02 mA/mm² and 0.15+/−0.02 mA/mm². The transverse current wasapplied through a single channel with a sinusoidal waveform, 10 Vpp/66microamperes peak-to-peak (μApp) with a 5-V DC offset, a frequency of100 Hz, for 15 hours.

FIG. 44E shows a sample with good strength and a rough finish. Theelectrodeposition current was 0.60+/−0.02 mA/mm². The transverse currentwas applied through a single channel with a sinusoidal waveform at 10Vpp/66 μApp with a 5 V DC offset, a frequency of 100 Hz, for 15 hours.

D. Joining Steel to Steel Via Fe—Sn Alloy

In a further example, two pieces of mild steel (5″×1″×0.032″) are joinedwith Fe—Sn from a corroding particle anode. The transverse current isapplied through a single channel is applied at 10 MHz for 8 hours usinga Teflon™ applicator.

Example 16—Joining Aluminum Workpieces with Nickel Gel Electrolyte

This example explores the effects of the frequency of transverse currenton electron density during the bonding process.

Two pieces of aluminum, each 1″×5″×0.032″, are joined using a nickelsulfate (NiSO₄) gel electrolyte. The edges of the aluminum workpiece arezincated before deposition to promote nickel adhesion despite the nativealuminum oxide layer. A Teflon™ applicator holds the electrolyte overthe junction between the workpieces and delivers the transverse currentto frequencies up to 10 GHz with losses less than 15 dbm. The applicatorincludes nickel anodes and two electrical contact points with theworkpieces, one on each workpiece less than 1 cm on either side of thejunction between the workpieces. The phase-matched transverse current isapplied at the midpoint of the length of each workpiece at 1.42 Vpp. Thetransverse current is cycled on for 0.1 s and off for 0.5 s, enough toaffect a strong joining without generating a an unwanted, continuousradio frequency.

The viscous electrolyte allows deposition nickel outside a conventionalbath and propagates the transverse current at lower conductivity withless attenuation than water. The propagation speed of the transversecurrent is calculated to be 6×10⁹ cm/sec, based fast impedancemeasurements of the effective permittivity for the electrolyte (about25).

FIG. 45 shows the electric field strength at an instant in time for adevice 4500 containing the aluminum workpieces 4510, 4511 at anapplicator 4530, which defines the “origin.” The energy distribution ofa 1-GHz transverse current produces a standing wave with nodes 4513,4515 and anti-nodes 4512, 4514, 4516. With no DC offset to theelectrodeposition or the transverse currents, electrodeposition occursat the red areas 4512, 4516; Corrosion occurs at the blue area 4514,which has the opposite polarity of the red areas 4512, 4516. With a DCoffset less than or equal to the Vpp of the transverse current, the Vppremains unchanged.

FIG. 46 shows the time-averaged energy density for a 1-GHz transversecurrent in a device 4600 containing the aluminum workpieces 4610, 4611at an applicator 4630, which defines the “origin.” The standing wave hasnodes 4613, 4615 and antinodes 4612, 4614, 4616. When the Vpp of thetransverse current is greater than the voltage of the DC offset, moredeposition or corrosion occurs at nodes 4613, 4615 than at theanti-nodes 4612, 4614, 4616.

Referring to FIG. 47, a transverse current is applied at a frequency of1.35 GHz in a device 4700, to workpieces 4710, 4711 at an applicator4730, which defines the “origin.” The standing wave produces nodes 4713,4715, 4717, 4719 and anti-nodes 4712, 4714, 4716, 4718, 4720.

Referring to FIG. 48, a transverse current is applied at a frequency of1.6 GHz in a device 4800, to workpieces 4810, 4811 at an applicator4530, which defines the “origin.” The standing wave produces nodes 4813,4815, 4817, 4819, 4821, 4823 and anti-nodes 4812, 4814, 4816, 4818,4820, 4822, 4824.

Referring to FIG. 49, a transverse current is applied at a frequency of220 MHz in a device 4900, to workpieces 4910, 4911 abutting at anapplicator 4530, which defines the “origin.” The ratio of the transversecurrent wave and the junction length causes the workpieces at the origin4914 to behave like an electrical short with low impedance. The ends ofthe workpiece 4912, 4916 terminate and behave like an open circuit,causing energy buildup. The length of the junction corresponds to halfthe transverse current wavelength, and the second frequency correspondsto one full period of the transverse current wavelength.

Referring to FIG. 50, a transverse current is applied at a frequency of480 MHz in a device 5000, to workpieces 5010, 5011 at an applicator4530, which defines the “origin.” The workpieces 5010, 5011 at theorigin 5014 experience a large increase in impedance, with localizedenergy buildup. The high energy density at the edges 5012, 5016 isweaker at 1λ.

Comparatively, the anti-node distribution for the 1.33-GHz transversecurrent is preferred for deposition (FIG. 47). The 1-GHz is too broadand intense (FIG. 45) and the energy distribution of 1.6-GHz transversecurrent is too uneven (FIG. 48). Above 1-GHz, the periodic transversecurrent artificially changes the rate of deposition points along thejunction, increasing the parallel electric field strength and preventinghigh current density areas. At frequencies of 1, 1.33 or 1.6 GHz, thetransverse current origin corresponds to an anti-node 100% of the time.There, the transverse current signal may be turned so the workpiecesurface at the origin is does not experience an anti-node. The higherfrequency transverse current may cause stronger bonds between the twoworkpieces because energy is better distributed, while the lowerfrequencies could cause a redistribute metal.

In laboratory samples, anti-nodes on either side of the junction are notbe identical. Differences in the phase on the electrodes arise fromthese asymmetries. These differences change as new metal is deposited.Cycling the transverse current helps avoid forming artificial roughspots.

Shifting the transverse current through several frequencies changes thestanding wave, so that nodes and antinodes fall on different positionsof the workpieces. The corrosion and deposition processes are thendistributed over the surface of the workpiece. A smooth finish isachieved on a deposit, particularly for high frequencies and withoutelectrodeposition signal modulation.

Example 17—Battery Healing

This example explores battery healing using the disclosed method.Li-metal coin cells are constructed inside a glove box under ananhydrous and oxygen-free inert argon atmosphere. The anode comprisesLi-foil and the electrolyte is a 1:1 mixture of ethylene carbonate anddimethyl carbonate with dissolved LiPF₆ at a concentration between 0.2 Mand 1.0 M. The coin cells are loaded into a charge-discharge cell todeliver impedance-regulated AC energy from a battery control unit to thecoin cell. During both charge and discharge cycles (deposition anddissolution), the transverse current signal is applied over the standardcharge/discharge potentials. Both processes involve Li diffusion throughthe solid electrolyte interphase. Electrical contact is made between thecharge-discharge cell and the coin cell.

In one instance, a centered 1-mm pin contacts the anode surface. The pinis centered inside a 1-mm thick conductive ring with a radius equal tothe coin cell's anode surface. Filling the space between the pin and thecoin cell is a polytetrafluoroethylene (PTFE) disk. The three componentsare brought into direct contact with the anode face of the coin cellinside the charge-discharge cell. The transverse current signaloriginates at the pin. The ring may be connected to ground or to asecond transverse current channel. The dielectric PTFE facilitatesuniform propagation of AC signal.

In another instance, both the pin and ring are separate transversecurrent channels, providing a transverse current of 2.4 GHz at a 180°phase offset. At the pin originates a −12 dbm sinusoidal wave and alongthe ring originates a −8 dbm sinusoidal wave. Over two minutes, thepowers at each channel are reversed, shifting the interference patternsmoves that sweeps the current density over the surface and encourageslateral movement of ions through the solid electrolyte interphase. Thissweeping discourages fixed ion channels from forming.

In still another instance, the transverse current channel at the pinuses no repeating waveform. Instead a continuously variable waveform isemitted that accounts for the constant constructive and destructiveinterference between incident energy from the pin and reflected energyfrom the outer edges of the anode. At areas of constructiveinterference, the localized potential exceeds the thermodynamic boundaryfor Li deposition or dissolution. Areas of destructive interference donot exceed this boundary, so deposition or dissolution lessens. As thetransverse current signal changes, the locations of these constructiveand destructive points change at a controlled rate similar to the ionicmobility of lithium ions.

With the pin contact, transverse current (incident AC energy) from thecharge-discharge cell is distributed radially and uniformly from thecenter to the outer edge of the Li-foil. When the wavelength of theincident energy is long compared to the radius of the anode, the ACpotential is roughly the same across the entire surface. When thewavelengths are similar to dimensions of the anode, reflections affectthe energy density and surface potential changes.

During the charging process, when Li-ions migrate from the electrolytethrough the solid electrolyte interphase and deposit onto the Li anode,the electromagnetic field is increased parallel to the foil surface.This increase aids lateral movement of Li+ ions in the solid electrolyteinterphase. The uniformity of the solid electrolyte interphase may bebetter maintained to achieve stability over increased number ofcharge/discharge cycles.

Having described several embodiments, it will be recognized by thoseskilled in the art that various modifications, alternativeconstructions, and equivalents may be used without departing from thespirit of the disclosure. And several well-known processes and elementshave not been described to avoid unnecessarily obscuring the embodimentsdisclosed. So the above description should not be taken as limiting thedocument.

Those skilled in the art will appreciate that the disclosed embodimentsteach for example and not by limitation. Therefore, the matter in theabove description or shown in the drawings should be interpreted asillustrative and not in a limiting sense. These claims should cover allgeneric and specific features described, and all statements of thepresent method and system, which, as a matter of language, might be saidto fall therebetween.

Exemplary Embodiments

The following is a listing of exemplary embodiments for methods andapparatuses disclosed herein:

-   1. A method comprising:    -   inducing a first current between a source of a countercharge and        a first electrode, the first current being through an        electrolyte;    -   inducing a second current across the first electrode, the second        current being transverse to the first current, and the second        current inducing a relativistic charge across the first        electrode.-   2. The method of claim 1, wherein the first electrode is a working    electrode.-   3. The method of claims 1-2, the electrolyte comprising a metal, the    first electrode having a void with a metal edge, the relativistic    charge causing a metal-metal bond to form between metal from the    electrolyte and the metal edge to thereby fill the void.-   4. The method of claim 3, wherein the void is a crack, crevice, or    fracture in the first electrode.-   5. The method of claim 3, the void forming a gap between a first    portion of the first electrode, the first portion having a first    edge of the metal edge, and a second portion of the first electrode,    the second portion with a second edge of the metal edge proximate    the first edge, the relativistic charge causing the metal-metal bond    to form between metal from the first edge and metal from the    electrolyte and between metal from the second edge and metal from    the electrolyte, the bonded metals thereby bridging the gap to form    a unified electrode of the first portion and the second portion.-   6. The method of claims 1-5, wherein the source of a countercharge    is an electrode counter to the first electrode.-   7. The method of claims 1-6, wherein the electrolyte comprises a    metal and one or more species selected from the group consisting of    water, ammonium salts, metal chlorides, metal sulfates, ionic    liquids, ionogels, and any combination thereof.-   8. The method of claim 7, wherein the electrolyte comprises an ionic    liquid, and the ionic liquid is a room temperature ionic liquid.-   9. The method of claim 8, wherein the room-temperature ionic liquid    is 1-ethyl-3-methylimidazolium chloride.-   10. The method of claims 1-9, wherein the electrolyte comprises    metal particles.-   11. The method of claims 1-10, wherein the second current is chosen    from an alternating current (AC) second current, or a combination of    an AC second current and a direct current (DC) second current.-   12. The method of claim 11, wherein the second current is the    combination of the AC second current and the DC second current, the    DC second current offsetting the AC second current by an amount less    than an electrochemical breakdown of the electrolyte.-   13. The method of claims 1-12, the second current having a waveform    comprising a plurality of waveforms based on harmonics of one or    more frequencies at which the electrolyte or the first electrode    exhibits absorption of the one or more frequencies.-   14. The method of claim 13, the second current having a phase offset    of about 90° between an onset frequency voltage and an output    amperage.-   15. The method of claims 1-14, further comprising applying a signal    cancellation to reduce a far-field radiation from the first    electrode.-   16. The method of claims 1-15, the second current having a period    similar to a diffusion rate of a component in the electrolyte.-   17. A method comprising:    -   inducing an electric field between a source of a countercharge        and a first electrode, the electric field having field lines        through an electrolyte;    -   inducing a potential across a surface of the first electrode,        the induced potential bending the field lines proximate the        surface such that metal from the electrolyte follows a path of        the bent field lines to deposit the metal onto the surface.-   18. The method of claim 17, wherein the first electrode is a working    electrode.-   19. The method of claims 17-19, the first electrode having a void    with a metal edge, the induced potential causing a metal-metal bond    to form between metal from the electrolyte and the metal edge to    thereby fill the void.-   20. The method of claim 19, wherein the void is a crack, crevice, or    fracture in the first electrode.-   21. The method of claim 19, the void forming a gap between a first    portion of the first electrode, the first portion having a first    edge of the metal edge, and a second portion of the first electrode,    the second portion with a second edge of the metal edge proximate to    the first edge, the relativistic charge causing the metal-metal bond    between metal from the first edge and metal from the electrolyte and    between metal from the second edge and metal from the electrolyte,    the bonded metals to thereby bridging the gap to form a unified    electrode of the first portion and the second portion.-   22. The method of claims 17-21, wherein the source of a    countercharge is an electrode counter to the first electrode.-   23. The method of claims 17-22, wherein the electrolyte comprising    one or more species selected from the group consisting of water,    quaternary ammonium salts, metal chlorides, ionic liquids, ionogels,    and any combination thereof.-   24. The method of claim 23, wherein the electrolyte comprises an    ionic liquid, and the ionic liquid is a room temperature ionic    liquid.-   25. The method of claim 24, wherein the room-temperature ionic    liquid is 1-ethyl-3-methylimidazolium chloride.-   26. The method of claims 17-25, wherein the electrolyte comprises    metal particles.-   27. The method of claims 17-26, wherein the second current is chosen    from an alternating current (AC) second current, or a combination of    an AC second current and a direct current (DC) second current.-   28. The method of claims 17-27, the induced potential having a    waveform comprising a plurality of waveforms based on harmonics of    one or more frequencies at which the electrolyte or the first    electrode exhibits absorption at the one or more frequencies.-   29. The method of claim 28, the induced potential having a phase    offset of about 90° between an onset frequency and an output    amperage.-   30. The method of claims 17-29, further comprising applying a signal    cancellation to reduce a far-field radiation from the first    electrode.-   31. The method of claims 17-30, the induced potential having a    period similar to a diffusion rate of a component in the    electrolyte.-   32. A method comprising: inducing a potential across a surface of an    electrode in the presence of a chemical potential between an    electrolyte and the surface of the electrode, the induced potential    relativistically charging the surface of the electrode.-   33. The method of claim 32, the relativistic charge causing a    metal-metal bond to form between metal from the electrolyte and    metal on the surface.-   34. The method of claim 33, the electrode having a void with a metal    edge, the relativistic charge causing the metal-metal bond between    metal from the electrolyte and the metal edge to thereby fill the    void.-   35. The method of claim 34, the void forming a gap between a first    portion of the electrode, the first portion having a first edge of    the metal edge, and a second portion of the electrode, the second    portion with a second edge of the metal edge proximate to the first    edge, the relativistic charge causing the metal-metal bond to form    between metal from the first edge and metal from the electrolyte and    between metal from the second edge and metal from the electrolyte,    the bonded metals to thereby bridging the gap to form a unified    electrode of the first portion and the second portion.-   36. The method of claims 32-35, wherein the electrolyte comprises    metal and one or more species selected from the group consisting of    water, quaternary ammonium salts, metal chlorides, ionic liquids,    ionogels, and any combination thereof.-   37. The method of claims 32-36, wherein the electrolyte comprises    metal particles.-   38. The method of claims 32-37, wherein the induced potential is    chosen from an alternating current (AC) induced potential, or a    combination of an AC induced potential and a direct current (DC)    induced potential.-   39. The method of claim 38, wherein the induced potential is the    combination of the AC induced potential and the DC induced    potential, the DC induced potential offsetting the AC induced    potential by an amount less than an electrochemical breakdown of the    electrolyte.-   40. The method of claims 32-39, the induced potential having a    waveform comprising a plurality of waveforms based on harmonics of    one or more frequencies at which the electrolyte or the electrode    exhibits absorption at the one or more frequencies.-   41. The method of claim 40, wherein the induced potential comprises    a phase offset of about 90° between an onset frequency and an output    amperage.-   42. The method of claims 32-41, further comprising applying a signal    cancellation to reduce a far-field radiation from the electrode.-   43. The method of claims 32-42, the induced potential having a    period similar to a diffusion rate of a component in the    electrolyte.-   44. The method of claims 1-43, wherein the first electrode comprises    at least two galvanically reactive metals meeting a junction, the    second current reducing corrosion at the junction.-   45. The method of claim 44, wherein the second current distributes    charge away from grain boundaries on the surface of the first    electrode and avoids corrosive pitting at the surface of the first    electrode.-   46. The method of claims 1-43, wherein the first current has a    positive potential sufficient to corrode away a rough feature at the    surface of the first electrode.-   47. The method of claim 46, wherein the first current is applied    with a low current density, a pulsed current density, or a    combination of a low, pulsed current density.-   48. The method of claims 1-31, wherein metal from the electrolyte    bonds to a vacant site on the surface of the first electrode or the    source for a countercharge and not to a previously bonded metal.-   49. The method of claim 48, wherein a membrane is disposed between    the source for a countercharge and the first electrode, the source    for a countercharge comprising LiM_(x)O_(y), the first electrode    comprising carbon or Li⁰, the metal from the electrolyte comprising    Li+, and the previously-bonded metal comprising Li⁰.-   50. A corroding electrode comprising one or more metal species    selected from the group consisting of metal particles, metal ions,    and combinations thereof;    -   wherein the corroding electrode dissolves when a first current        is applied between the corroding electrode and a first electrode        through an electrolyte, thereby suspending the one or more metal        species into the electrolyte.-   51. The corroding electrode of claim 50, further comprising one or    more ceramic particles or dielectric polymers.-   52. The corroding electrode of claims 50-51, wherein the corroding    source of a countercharge is formed by being pressed together into a    solid body.-   53. The corroding electrode of claims 50-52, wherein the metal    particles have grain sizes selected to grain sizes of the first    electrode.-   54. The corroding electrode of claims 50-53, comprising metal    particles having rough or non-symmetric dimensions.-   55. The corroding electrode of claims 50-54, comprising metal    particles having spherical dimensions and a uniform surface energy.-   56. The corroding electrode of claims 50-55, comprising metal    particles having an elongated dimension, which aligns with a second    current induced across the first electrode, the second current being    transverse to the first current, and the second current inducing a    relativistic charge across the first electrode.-   57. The method of claims 1-31, wherein the source of a countercharge    is a corroding electrode of claims 50-56.-   58. A device comprising:    -   a source of a countercharge, and    -   a first electrode in electrical communication through an        electrolyte with the source of a countercharge;    -   wherein a first current is induced through the electrolyte        between the source of a countercharge and the first electrode;        and    -   wherein a second current is induced across the first electrode,        the second current being transverse to the first current, and        the second current inducing a relativistic charge across the        first electrode.-   59. The device of claim 58, wherein the first electrode is a working    electrode.-   60. The device of claims 58-59, the electrolyte comprising a metal,    the first electrode having a void with a metal edge, the    relativistic charge causing a metal-metal bond to form between metal    from the electrolyte and the metal edge to thereby fill the void.-   61. The device of claim 60, wherein the void is a crack, crevice, or    fracture in the first electrode.-   62. The device of claim 60, the void forming a gap between a first    portion of the first electrode, the first portion having a first    edge of the metal edge, and a second portion of the first electrode,    the second portion with a second edge of the metal edge proximate    the first edge, the relativistic charge causing the metal-metal bond    to form between metal from the first edge and metal from the    electrolyte and between metal from the second edge and metal from    the electrolyte, the bonded metals thereby bridging the gap to form    a unified electrode of the first portion and the second portion.-   63. The device of claims 58-62, wherein the source of a    countercharge is an electrode counter to the first electrode.-   64. The device of claims 58-63, wherein the electrolyte comprises a    metal and one or more species selected from the group consisting of    water, quaternary ammonium salts, metal chlorides, ionic liquids,    ionogels, and any combination thereof.-   65. The device of claim 64, wherein the electrolyte comprises an    ionic liquid, and the ionic liquid is a room temperature ionic    liquid.-   66. The device of claim 65, wherein the room-temperature ionic    liquid is 1-ethyl-3-methylimidazolium chloride.-   67. The device of claims 58-66, wherein the electrolyte comprises    metal particles.-   68. The device of claims 58-67, wherein the second current is chosen    from an alternating current (AC) second current, or a combination of    an AC second current and a direct current (DC) second current.-   69. The device of claim 68, wherein the second current is the    combination of the AC second current and the DC second current, the    DC second current offsetting the AC second current by an amount less    than an electrochemical breakdown of the electrolyte.-   70. The device of claims 58-69, further comprising a waveform    generator to provide the second current with a waveform comprising a    plurality of waveforms based on harmonics of one or more frequencies    at which the electrolyte or the first electrode exhibits absorption    of the one or more frequencies.-   71. The device of claims 58-70, further comprising a signal canceler    to reduce a far-field radiation from the first electrode.-   72. The device of claims 58-71, the second current having a period    similar to a diffusion rate of a component in the electrolyte.-   73. A device comprising:    -   a source of a countercharge, and    -   a first electrode in electrical communication through an        electrolyte with the source of a countercharge;    -   wherein an electric field is induced between the source of a        countercharge and the first electrode, the electric field having        field lines through the electrolyte; and    -   wherein a potential is induced across a surface of the first        electrode, the induced potential bending the field lines        proximate the surface such that metal from the electrolyte        follows a path of the bent field lines to deposit the metal onto        the surface.-   74. The device of claim 73, wherein the first electrode is a working    electrode.-   75. The device of claims 73-75, the first electrode having a void    with a metal edge, the induced potential causing a metal-metal bond    to form between metal from the electrolyte and the metal edge to    thereby fill the void.-   76. The device of claim 75, wherein the void is a crack, crevice, or    fracture in the first electrode.-   77. The device of claim 75, the void forming a gap between a first    portion of the first electrode, the first portion having a first    edge of the metal edge, and a second portion of the first electrode,    the second portion with a second edge of the metal edge proximate to    the first edge, the relativistic charge causing the metal-metal bond    between metal from the first edge and metal from the electrolyte and    between metal from the second edge and metal from the electrolyte,    the bonded metals to thereby bridging the gap to form a unified    electrode of the first portion and the second portion.-   78. The device of claims 73-77, wherein the source of a    countercharge is an electrode counter to the first electrode.-   79. The device of claims 73-78, wherein the electrolyte comprises    one or more species selected from the group consisting of water,    quaternary ammonium salts, metal chlorides, ionic liquids, ionogels,    and any combination thereof.-   80. The device of claim 79, wherein the electrolyte comprises an    ionic liquid, and the ionic liquid is a room temperature ionic    liquid.-   81. The device of claim 80, wherein the room-temperature ionic    liquid is 1-ethyl-3-methylimidazolium chloride.-   82. The device of claims 73-81, wherein the electrolyte comprises    metal particles.-   83. The device of claims 73-82, wherein the second current is chosen    from an alternating current (AC) second current, or a combination of    an AC second current and a direct current (DC) second current.-   84. The device of claims 73-83, further comprising a waveform    generator to provide the induced potential with a waveform    comprising a plurality of waveforms based on harmonics of one or    more frequencies at which the electrolyte or the first electrode    exhibits absorption at the one or more frequencies.-   85. The device of claims 73-84, further comprising a signal canceler    to reduce a far-field radiation from the first electrode.-   86. The device of claims 73-85, the induced potential having a    period similar to a diffusion rate of a component in the    electrolyte.-   87. A first electrode, wherein a potential is induced across a    surface of the first electrode in the presence of a chemical    potential between an electrolyte and the surface of the first    electrode, the induced potential relativistically charging the    surface of the first electrode.-   88. The first electrode of claim 87, the relativistic charge causing    a metal-metal bond to form between metal from the electrolyte and    metal on the surface.-   89. The first electrode of claim 88, the first electrode having a    void with a metal edge, the relativistic charge causing the    metal-metal bond between metal from the first electrolyte and the    metal edge to thereby fill the void.-   90. The first electrode of claim 89, the void forming a gap between    a first portion of the first electrode, the first portion having a    first edge of the metal edge, and a second portion of the first    electrode, the second portion with a second edge of the metal edge    proximate to the first edge, the relativistic charge causing the    metal-metal bond to form between metal from the first edge and metal    from the electrolyte and between metal from the second edge and    metal from the electrolyte, the bonded metals to thereby bridging    the gap to form a unified electrode of the first portion and the    second portion.-   91. The first electrode of claims 87-90, wherein the electrolyte    comprises metal and one or more species selected from the group    consisting of water, quaternary ammonium salts, metal chlorides,    ionic liquids, ionogels, and any combination thereof.-   92. The first electrode of claims 87-91, wherein the electrolyte    comprises metal particles.-   93. The first electrode of claims 87-92, wherein the induced    potential is chosen from an alternating current (AC) induced    potential, or a combination of an AC induced potential and a direct    current (DC) induced potential.-   94. The first electrode of claim 93, wherein the induced potential    is the combination of the AC induced potential and the DC induced    potential, the DC induced potential offsetting the AC induced    potential by an amount less than an electrochemical breakdown of the    electrolyte.-   95. The first electrode of claims 87-94, the induced potential    having a waveform comprising a plurality of waveforms based on    harmonics of one or more frequencies at which the electrolyte or the    electrode exhibits absorption at the one or more frequencies.-   96. The first electrode of claims 87-95, the induced potential    having a period similar to a diffusion rate of a component in the    electrolyte.-   97. A device comprising:    -   a main control unit comprising a power supply and a power        modulator;    -   an electrode applicator unit, comprising at least one source of        a countercharge and a plurality of channels for flowing an        electrolyte through the electrode applicator unit, the electrode        applicator unit being connected to the main control unit;    -   a current collector cable connected to the main control unit;        and    -   a power control unit connected to the main control unit, which        power control unit applies a first current between a first        electrode and the at least one source of a countercharge through        the electrolyte, the power control unit inducing a second        current across the first electrode, the second current being        transverse to the first current, and the second current inducing        a relativistic charge across the first electrode.-   98. The device of claim 97, wherein the main control unit further    comprises a computer for executing instructions stored on a computer    readable medium.-   99. The device of claim 98, wherein the power modulator and the    power control unit are controlled by the computer.-   100. The device of claims 97-99, wherein the main control unit    further comprises an electrolyte storage tank, at least one pump,    and tubing connected to the electrolyte storage tank, the at least    one pump, and the electrode applicator unit; thereby flowing the    electrolyte from the electrolyte storage tank through the tubing    into the plurality of channels of the electrode applicator unit.-   101. The device of claims 97-100, wherein the electrode applicator    unit further comprises a heating unit or a cooling unit for    modulating a temperature of the electrolyte within the channels of    the electrode applicator unit.-   102. The device of claims 97-101, wherein the current collector    cable further comprises leads for attaching to the first electrode.-   103. The device of claim 56-86 or 97-102, wherein the at least one    source of a countercharge comprises a corroding electrode of claims    50-56.-   104. The device of claim 56-86 or 97-102, wherein the device    performs a method of claims 1-49.

1-32. (canceled)
 33. A method for operating an electrochemical cell, themethod comprising: obtaining an impedance measurement of theelectrochemical cell; and adjusting, based on the impedance measurement,an alternating current electric waveform conducted on an electrode ofthe electrochemical cell to control deposition of metal from anelectrolyte onto the electrode and reduce the formation of dendrites.34. The method of claim 1, wherein the alternating current electricwaveform relativistically charges the electrode to bend a field line ofa charge current through the electrolyte to control the deposition ofmetal onto the electrode.
 35. The method of claim 1, wherein thealternating current electric waveform is selected from the groupconsisting of sinusoid, square, triangle, ramp, saw tooth, andcombinations thereof.
 36. The method of claim 1, wherein the alternatingcurrent electric waveform comprises a plurality of waveforms based onharmonics of one or more frequencies at which the electrode exhibitsabsorption of the one or more frequencies.
 37. The method of claim 36,wherein the plurality of waveforms is further based on the impedancemeasurement of the electrochemical cell.
 38. The method of claim 37,wherein the impedance measurement is a linear impedance response to aprobe signal superimposed on a charge current, the linear impedanceresponse based on a topography of a surface of the electrode.
 39. Themethod of claim 38 further comprising: comparing the linear impedanceresponse to a stored impedance measurement of the electrochemical cellto determine a change in the impedance measurement of theelectrochemical cell.
 40. The method of claim 33, wherein theelectrochemical cell is a lithium-based battery.
 41. The method of claim33, wherein the electrochemical cell is a lead-acid battery and thealternating current electric waveform on the electrode is composed toreflect off an inner wall of the electrochemical cell.
 42. The method ofclaim 33, wherein inducing the alternating current electric waveformcomprises sweeping through a plurality of frequencies.
 43. The method ofclaim 33, wherein the alternating current electric waveform is conductedacross the electrode of the electrochemical cell.
 44. An apparatuscomprising: a waveform generator coupled with an electrode, the waveformgenerating device superimposing a probe signal on a charge signal toobtain an impedance measurement of an electrochemical cell and inducing,based on the impedance measurement, an alternating current electricwaveform on the electrode of the electrochemical cell to controldeposition of metal from an electrolyte onto the electrode and reducethe formation of dendrites on the electrode.
 45. The apparatus of claim44, wherein the alternating current electric waveform comprises aplurality of waveforms based on harmonics of one or more frequencies atwhich the electrolyte or the electrode exhibits absorption of the one ormore frequencies.
 46. The apparatus of claim 44, wherein the impedancemeasurement is a linear impedance response based on a topography of asurface of the electrode.
 47. The apparatus of claim 46, wherein thelinear impedance response is inversely proportional to a smoothness ofthe surface of the electrode.
 48. The apparatus of claim 44, wherein theelectrode is a cathode of a lithium-ion battery, the waveform generatorinducing the alternating current electric waveform on the electrodeduring charging of the lithium-ion battery.
 49. The apparatus of claim44, wherein the electrode is a cathode or anode of a lead-acid battery,the waveform generator inducing the alternating current electricwaveform to reflect off an inner wall of the lead-acid battery.
 50. Theapparatus of claim 44, wherein inducing the alternating current electricwaveform comprises combining a direct current waveform with thealternating current electric waveform.
 51. The apparatus of claim 44,wherein the waveform generator selects the alternating current electricwaveform from a group consisting of sinusoid, square, triangle, ramp,saw tooth, and combinations thereof.
 52. The apparatus of claim 44,wherein the alternating current electric waveform relativisticallycharges the electrode to cause a bend in a field line of a chargecurrent through the electrolyte to control the deposition of metal ontothe electrode.